Peripheral vasodilator and cardiac properties of the 1,5-benzothiazepine calcium antagonist analog, TA-3090, in dogs

Diltiazem, a 1,5-benzothiazepine, has demonstrated efficacy in the treatment of numerous cardiovascular diseases. TA-3090, a newly synthetized 1,5-benzothiazepine compound was studied in open-chest anesthetized dogs to characterize its hemodynamic properties, to compare it with diltiazem, and finally to correlate hemodynamic properties and plasma level concentrations. Anesthetized open-chest dogs were instrumented with electronic devices and fluid-filled catheters to monitor cardiac, coronary, and peripheral hemodynamic changes. A cumulative intravenous bolus administration of TA-3090 (n = 16) or diltiazem (n = 15) (15, 50, 200, and 400 micrograms/kg) was carried out, and blood samples were taken before and 5 min following each dose administration. Hemodynamic changes were followed for 30 min after each administration, at which time most hemodynamic parameters were back to baseline levels. The results indicate that both TA-3090 and diltiazem elicit slight peripheral and coronary vasodilator properties at low doses (15 and 50 micrograms/kg). With higher dosage, hemodynamic effects were maximal: coronary blood flow increased by 75%, arterial pressure decreased by 25%, and reflex positive inotropic effects were also observed. Heart rate was significantly reduced (10%). Comparison between TA-3090 and diltiazem indicates that both drugs elicit coronary vasodilator selectivity and TA-3090 has a prolonged duration of action compared with that of diltiazem. A straightforward relationship is demonstrated between vasodilator properties and plasma levels of either TA-3090 or diltiazem. Our data suggest that with plasma levels between 40 and 80 ng/mL, significant hemodynamic changes were observed with TA-3090. Changes of heart rate were not correlated with plasma levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of vascular Na-K pump with subpressor angiotensin II in rats.

The effect of subpressor doses of angiotensin II (ANG II) on vascular Na-K pump activity and Na-H exchange, two transmembrane signals of trophic stimulation of vascular muscle, was investigated. Male Sprague-Dawley rats (350-400 g) were given subpressor doses of ANG II by osmotic minipump intraperitoneally for 24 hr or 7-10 days. Control rats received sham procedure/vehicle infusion. Na-K pump activity (86Rb uptake), total and intracellular (Li exchange at 4 degrees C) Na content, and amiloride-sensitive and -insensitive Na uptake of aortas were measured ex vivo. Ouabain-sensitive 86Rb uptake of aortas of rats receiving 80-100, 160-180, and 240-260 ng/kg.min-1 of ANG II for 24 hr was 26.6 +/- 3.5, 28.8 +/- 3.4, and 29.1 +/- 2.6 nmol/mg dry wt.15 min-1 (mean +/- SD, n = 7-12), respectively, compared with 25.2 +/- 3.8 in controls (n = 23, P less than 0.01). These increases were maintained at 7-10 days. After 24 hr and 7-10 days of ANG II treatment, the total Na content of aortas was increased by 9.2% (P less than 0.01) and 7.6% (P less than 0.02), respectively, without a change in intracellular Na content, indicating accumulation of excess extracellular Na. Total and amiloride-sensitive Na uptake of the aorta was unchanged after 24 hr or 7-10 days of ANG II administration. The dry weight of anatomically defined segments of the aorta was 40 +/- 3.8 mg/kg body wt (n = 25) after 24 hr and 42 +/- 4.4 (n = 20) after 7-10 days of ANG II administration, compared with 37 +/- 4.8 (n = 15, P less than 0.05) and 37 +/- 4.9 (n = 17, P less than 0.01) in appropriate controls. Increased Na-K pump activity may signal the onset of trophic stimulation of vascular muscle by ANG II.     

Fat energy use and plasma lipid changes associated with exercise intensity and temperature

The effect of 60 min of exercise at two intensities (50 and 60% VO2max) and temperatures (0 and 22 degrees C) on changes (delta) in plasma lipids [triglycerides (TG), glycerol (GLY), total cholesterol (TC), and HDL-cholesterol (HDL-C)] was examined. Subjects were 10 men aged 27 +/- 7 years (VO2max = 3.81 +/- 0.45 1 min, % fat = 12.2% +/- 7.1%). VO2 and respiratory exchange ratio results indicated that total energy and fat energy use were similar at the two temperatures. Changes in plasma volume (%delta PV) were different (P less than 0.05) at the two temperatures (22 degrees C: -2.3% vs 0 degrees C: 1.1%). Combining the data at each temperature revealed that the increases in concentrations were greater (P less than 0.05) at 22 degrees C (delta TG = 0.22, delta GLY = 0.20, delta TC = 0.14, delta HDL-C = 0.05 mmol l-1) vs 0 degrees C (delta TG = 0.10, delta GLY = 0.12, delta TC = 0.05, delta HDL-C = 0.02 mmol l-1). Combining the data for each intensity revealed that the increases in concentration were greater (P less than 0.05) at 60% VO2max for delta TG and delta HDL-C. The 60% VO2max/22 degrees C bout produced greater changes (P less than 0.05) than all other bouts for delta TC and delta HDL-C (0.21 and 0.08 mmol l-1, respectively). Only delta TG and delta GLY were greater at 22 degrees C when adjusted for %delta PV. These metabolic and plasma lipid results indicate that cold exposure does not act synergistically with exercise to further stimulate fat metabolism.     

Pharmacodynamic and protective properties of a murine lipopolysaccharide-specific monoclonal antibody in experimental Pseudomonas aeruginosa pneumonia in mice.

We employed a Pseudomonas aeruginosa mouse pneumonia model to evaluate the ability of a murine monoclonal antibody (MAb) specific for the O-side chain of P. aeruginosa Fisher Immunotype-1 lipopolysaccharide (LPS) to achieve and sustain therapeutic levels in plasma and lung tissue, reduce bacterial populations in the lung, and prevent pneumonia-associated mortality. An IgG3 MAb (Y1-5A4) administered to mice i.v. over a dose range of 125-1,000 micrograms/mouse produced plasma and lung tissue levels at 2 hr of 61-507 micrograms/ml and 4.3-150 micrograms/g, respectively. The 1,000 micrograms MAb dose reduced bacterial counts in lung tissue (log10 cfu/g +/- S.D.) and blood (log10 cfu/ml +/- S.D.) 20 hr post-treatment (18 hr post-challenge) from 10.00 +/- 0.66 to 7.66 +/- 0.91 (P less than 0.01) and from 4.39 +/- 0.81 to less than 3.0, respectively. Administration of MAb to mice in doses of 125-500 micrograms 2 hr prior to a 3 x 50% lethal bacterial challenge produced significant protection against death, with a calculated 50% protective dose of 167 micrograms. Protection was noted following administration of 1,000 micrograms of MAb up to 6 hr after bacterial challenge (P less than 0.05, compared with untreated control). Histological examination of lung tissue from infected mice revealed less acute inflammation, necrosis, and hemorrhage in MAb-treated compared with untreated control animals and greater localization of Pseudomonas antigen within the phagocytic cells in alveolar space. These findings document the in vivo therapeutic efficacy of an LPS-specific IgG MAb in a murine model of acute P. aeruginosa pneumonia, based in part upon the achievability of effective MAb concentrations in plasma and lung tissue.     

Lipid profile in trained subjects undergoing complete food deprivation combined with prolonged intermittent exercise

Sixteen male subjects [18-21 years, maximal oxygen consumption (VO2max) = 59.2 ml.kg-1.min-1 +/- SEM 5.6] participated in a study to evaluate the effect of prolonged, complete food deprivation combined with physical effort, on plasma lipoprotein concentrations. The subjects were deprived of food for 81 h but were supplied with water: they walked for 10 h a day at 40% of VO2max, covering a total of 105 km. During this period the subjects' average mass decreased significantly (P less than 0.05) reflecting a marked catabolic process. Plasma concentration of low density lipoprotein-cholesterol [( LDL-C]) and triglycerides were significantly lower (P less than 0.05) and total cholesterol, high-density lipoprotein-cholesterol [( HDL-C]), and free fatty acid levels were significantly higher (P less than 0.05) at the end of the experimental period compared to the start. The ratio between plasma [HDL-C] to plasma [LDL-C] increased from 0.51 to 0.89 at the end of the exercise period, reflecting a marked anti-atherogenic effect. All changes were transient and reversible within 12 days of recovery.     

Kinetics of chylomicron triglyceride removal from plasma in rats: a comparison of the anesthetized and the unanesthetized states

The kinetics of chylomicron-TG removal were studied using an experimental method which allows measurements to be made under optimal physiological conditions. Chylomicrons, labeled with palmitic acid-(14)C, were constantly infused at a rate of 0.5 mg total lipid per min into chronically cannulated, unanesthetized, unrestrained rats which had been fasted for 18 hr. Serial blood samples were withdrawn from an arterial cannula during a 20 min infusion period and for 10 min following the infusion. Plasma lipoproteins were separated into two fractions in the ultracentrifuge, and the lipids were extracted. Radioactivity in the low-density fraction (d<1.006) was taken to represent chylomicron-TG radioactivity. Using this method we studied the influence of anesthesia on the kinetics of removal of chylomicron-TG. The following three phases of the radioactivity-time curve were plotted: (a) the increase in (14)C during infusion of chylomicrons, (b) the steady-state phase during the infusion, and (c) the decay of (14)C after chylomicron infusion was stopped. The values for the anesthetized rats failed to reach a steady-state phase during the course of the experiment. From the disappearance of (14)C following the end of the infusion, the apparent half time of removal of chylomicron-TG was estimated to be 2.8 +/- 0.37 min in unanesthetized rats, 4.5 +/- 0.37 min in rats anesthetized with sodium pentobarbital, and 4.4 +/- 0.44 min in rats anesthetized with halothane. Thus, two anesthetics with different physical properties markedly slowed the removal of chylomicron-TG from the circulation. The reduced rate may have resulted from alterations in cardiac output or distribution of blood flow induced by the anesthetic agents.     

Effect of fish oil diet on hepatic lipid metabolism in nonhuman primates: lowering of secretion of hepatic triglyceride but not apoB

African green monkeys were fed diets containing either 11% (by weight) fish oil or lard for 2.5 yr. To test the hypothesis that fish oil decreases hepatic secretion of triglyceride (TG) and apoB, livers from these animals were perfused with a fatty acid mixture [85% (w/w) oleate containing [14C]oleate and 15% n-3 containing [3H]eicosapentaenoic acid (EPA)] at a rate of 0.1 mumol fatty acid/min per g liver. Liver perfusate was sampled every 30 min during 4 h of recirculating perfusion. The concentration of triglyceride was similar for livers of animals of both groups and there was no difference between groups in the extent of incorporation of [3H]EPA or [14C]oleate into hepatic TG. While the secretion rate for the mass of TG was less in the fish oil-fed group (8.3 +/- 2.5 vs 18.3 +/- 4.4 mg/h per 100 g liver, P less than 0.05), the apoB secretion rate was similar (0.92 +/- 0.15 vs 1.01 +/- 0.13 mg/h per 100 g liver). Significantly less [3H]EPA was incorporated into secreted TG in the fish oil group (0.4 +/- 0.1 vs 1.0 +/- 0.1% infused dose/h; P less than 0.01). The rate of secretion of [14C]TG was similar for both groups (1.3 +/- 0.3 vs 1.4 +/- 0.1% infused dose/h for fish oil and lard groups, respectively). No significant diet-related differences in [3H]TG or [14C]TG fatty acid specific activity were observed for perfusate TG or hepatic TG. After perfusion, livers from fish oil-fed monkeys contained significantly more [3H]EPA in hepatic phospholipid than livers from lard-fed monkeys (19.5 +/- 1.8 vs 11.4 +/- 1.7% infused dose; P less than 0.01) although hepatic phospholipid mass concentrations were similar. The liver phospholipids of the fish oil group were enriched in n-3 fatty acid mass and were relatively depleted of oleate and linoleate. We conclude that although apoB secretion was unaffected, dietary fish oil significantly decreased hepatic TG secretion through relatively poor utilization of EPA for the synthesis of TG destined for secretion in VLDL; at the same time, increased incorporation of [3H]EPA into hepatic phospholipid accompanied the decreased incorporation into secreted TG and these events may be coupled.(ABSTRACT TRUNCATED AT 400 WORDS)     

Stressor-associated alterations in porcine plasma prolactin

Experiments were conducted to determine effects of restraint and thermal stressors on plasma prolactin (PRL) in castrated male pigs. A single 20-min restraining period in a restraining cage which prevented both movement and injury increased (P less than 0.05) plasma PRL when applied at either 0800 or 1600 hr. Exposure to 32 degrees C at 0800-1000 hr or at 1600-1800 hr produced more moderate increases (P less than 0.05). A combination of 20 min restraint and 2 hr at 32 degrees C produced a response similar to restraint alone. Twenty minutes after stressor application plasma PRL concentrations in pigs exposed to restraint or restraint +32 degrees C at 1600 h were greater (P less than 0.05) than concentrations measured in all other treatment groups at that time interval. However, there were no statistically significant differences in additional quantitative indices of the plasma PRL responses (maximal level, maximal change, or integrated response above basal levels) among restraint, 32 degrees C, or restraint +32 degrees C, nor between morning and afternoon applications of treatment. Such data do not provide, therefore, any strong evidence for stressor-dependent or circadian differences in plasma PRL response. A second study subjected castrated male pigs to 20 degrees C (controls), 20 +/- 12 degrees C (cyclic temperature, sine wave variation), 5 degrees C constant, and 5 +/- 12 degrees C cyclic for 20 days. After 6 days exposure to 5 degrees C constant or 5 +/- 12 degrees C cyclic there were decreases (P less than 0.05) of 59 and 67% respectively in plasma PRL when compared either with pretreatment levels or with levels in pigs at 20 or 20 +/- 12 degrees C. There were no differences in PRL responses between cyclic vs constant temperatures. These results are the first to indicate that plasma PRL in pigs is affected by acute restraint and thermal stressors.     

Protein turnover and amino acid transport kinetics in end-stage renal disease

Protein and amino acid metabolism is abnormal in end-stage renal disease (ESRD). Protein turnover is influenced by transmembrane amino acid transport. The effect of ESRD and hemodialysis (HD) on intracellular amino acid transport kinetics is unknown. We studied intracellular amino acid transport kinetics and protein turnover by use of stable isotopes of phenylalanine, leucine, lysine, alanine, and glutamine before and during HD in six ESRD patients. Data obtained from amino acid concentrations and enrichment in the artery, vein, and muscle compartments were used to calculate intracellular amino acid transport and muscle protein synthesis and catabolism. Fractional muscle protein synthesis (FSR) was estimated by the precursor product approach. Despite a significant decrease in the plasma concentrations of amino acids in the artery and vein during HD, the intracellular concentrations remained stable. Outward transport of the amino acids was significantly higher than the inward transport during HD. FSR increased during HD (0.0521 +/- 0.0043 vs. 0.0772 +/- 0.0055%/h, P < 0.01). Results derived from compartmental modeling indicated that both protein synthesis (118.3 +/- 20.6 vs. 146.5 +/- 20.6 nmol.min-1.100 ml leg-1, P < 0.01) and catabolism (119.8 +/- 18.0 vs. 174.0 +/- 14.2 nmol.min-1.100 ml leg-1, P < 0.01) increased during HD. However, the intradialytic increase in catabolism exceeded that of synthesis (57.8 +/- 13.8 vs. 28.0 +/- 8.5%, P < 0.05). Thus HD alters amino acid transport kinetics and increases protein turnover, with net increase in protein catabolism.     

Why does experimental insulin deficiency lead to a decrease in removal of very low density-triglyceride from plasma?

We have previously suggested that mechanisms other than reduced lipoprotein lipase (LPL) activity might contribute to the defect in plasma removal of very low density lipoprotein (VLDL)-triglyceride (TG) observed in insulin-deficient rats. To further evaluate this phenomenon, removal rates of TG in nonfractionated plasma, as well as in isolated lipoprotein fractions obtained from insulin-deficient and control rats, were compared in a new, sensitive in vivo bioassay system (estradiol-treated male rats with a consistently low endogenous VLDL-TG pool). Removal of TG in nonfractionated plasma from insulin-deficient rats was slower than that of control rats: 3.0 +/- 0.3 vs 1.6 +/- 0.2 min (P less than 0.001). No difference was found in removal rate of isolated VLDL-TG (2.5 +/- 0.3 vs 2.6 +/- 0.4 min), or in removal rates of TG carried in other lipoprotein fractions. We next determined the effect of injection into normal rats of aliquots of dialyzed lipoprotein-free (D greater than 1.215) plasma from insulin-deficient and control rats on the removal rate of normal VLDL-TG, and found that lipoprotein-free plasma from insulin-deficient rats significantly (P less than 0.01) prolonged removal of normal VLDL-TG (4.3 +/- 0.4 to 6.8 +/- 0.7 min). This same fraction did not interfere with the in vitro hydrolysis of normal VLDL-TG by post-heparin LPL. Thus, a factor in the D greater than 1.215 plasma fraction of insulin-deficient rats is present which interferes with the rate of removal of TG from plasma, unrelated to inhibition of LPL activity.     

Postprandial plasma lipoprotein changes in human subjects of different ages

Plasma lipoprotein changes were monitored for 12 hr after a fat-rich meal (1 g of fat/kg body weight) in 22 subjects (9 males, 13 females, 22-79 yr old). Plasma triglyceride, measured hourly, peaked once in some subjects, but twice or three times in others. The magnitude of postprandial triglyceridemia varied considerably between subjects (range: 650-4082 mg.hr/dl). Males tended to have greater postprandial triglyceridemia than females, and elderly subjects had significantly (P less than 0.05) greater postprandial triglyceridemia than younger subjects. Total plasma cholesterol, measured every three hr, increased significantly (6.0 +/- 2.1%) in 7 subjects, decreased significantly (7.1 +/- 1.2%) in 10 subjects, and remained unchanged in the remainder. Single spin ultracentrifugation and dextran sulfate precipitation procedures were used to quantitate triglyceride and cholesterol in triglyceride-rich lipoproteins (TRL, d less than 1.006 g/ml), low density lipoproteins (LDL), and high density lipoproteins (HDL). Plasma TRL and HDL triglyceride increased after the fat meal, while LDL triglyceride decreased at 3 hr but increased at 9 and 12 hr. TRL cholesterol increased postprandially, while LDL and HDL cholesterol decreased. Phospholipid (PL), free (FC) and esterified (EC) cholesterol measurements were carried out on the plasma and lipoprotein fractions of 8 subjects. Plasma PL increased significantly at 3, 6, and 9 hr after the fat-rich meal, due to increases in TRL and HDL PL. TRL CE increased postprandially, but a greater decrease in LDL and HDL CE caused plasma CE to be decreased. Plasma FC increased, predominantly due to an increase in TRL FC. Plasma concentrations of apolipoprotein A-I and apolipoprotein B both decreased after the fat-rich meal. The magnitude of postprandial triglyceridemia was inversely correlated with HDL cholesterol levels (r = -0.502, P less than 0.05) and positively correlated with age (r = -0.449, P less than 0.05), fasting levels of plasma triglyceride (r = 0.636, P less than 0.01), plasma apoB (r = 0.510, P less than 0.05), TRL triglyceride (r = 0.564, P less than 0.01), TRL cholesterol (r = 0.480, P less than 0.05) and LDL triglyceride (r = 0.566, P less than 0.01). Change in postprandial cholesterolemia was inversely correlated with fasting levels of HDL cholesterol (r = -0.451, P less than 0.05) and plasma apoA-I (r = -0.436, P less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)     

A comparison of chloride, bromide, and sucrose dilution volumes in neonatal pigs

Use of 36Cl, 82Br, and [3H]sucrose to estimate extracellular water volume was evaluated in 14 piglets (7-14 days old). 36Cl and 82Br were distributed in approximately the same volume, but a period of 5-6 hr after injection was required to reach equilibrium in the neonatal pig. Dilution volumes calculated before equilibration (2-5 hr) for 36Cl (326 +/- 11 ml/kg) and 82Br (328 +/- 13 ml/kg) were different from equilibration (6-8 hr) phase volumes (356 +/- 13 ml/kg and 355 +/- 13 ml/kg, respectively; P less than 0.001). A 3-hr sample estimated the same volume distribution calculated by extrapolation of the 6- to 8-hr period because of the relationship between the two slopes of the plasma clearance curves. After the 82Br and 36Cl had achieved equilibration, each was distributed in a volume equivalent to total body chloride space (362 +/- 29 ml/kg) measured by neutron activation; no statistical differences were found (P = 0.6). The early equilibration phase measured a 10% smaller, faster exchangeable fraction of total body Cl. Sucrose dilution volume (332 +/- 19 ml/kg) required multiple plasma samples for extrapolation and measured a dilution volume 7% smaller (P less than 0.05) than total body chloride space.     

Pituitary-adrenocortical and lymphocyte responses to bromocriptine-induced hypoprolactinemia, adrenocorticotropic hormone, and restraint in swine

A study was conducted with castrated male pigs (barrows) to evaluate effects of bromocriptine-induced hypoprolactinemia (6 days) on basal and adrenocorticotropic hormone (ACTH)-altered (single injection) pituitary-adrenocortical function, on lymphocyte proliferative responses, and on interleukin 2 production. In addition, the study was designed to measure the short time course of pituitary-adrenocortical and lymphocyte responses to ACTH and to a 30-min restraint stressor. Blood samples were taken via indwelling jugular catheters at -0.5, +0.5, +2, and +5 hr (with reference to time of acute treatment exposure) on Day 6 of the study. Lymphocyte responses were measured only at the 2-hr interval. Exposure (6 days) to bromocriptine (CB154) was associated with 53% reductions (P less than 0.05) in plasma prolactin (1.37 +/- 0.13 vs 0.60 +/- 0.04 vs 0.68 +/- 0.08 ng/ml) when averaged across all time intervals in control, CB154-treated, and CB154 + ACTH-treated pigs, respectively. The reductions in plasma prolactin were associated with a reduction (P less than 0.05) in basal plasma cortisol at only one time interval (+0.5 hr) when CB154-treated pigs were compared with controls (17.7 +/- 4.2 vs 26.9 +/- 3.2 ng/ml). CB154 had no effect on plasma ACTH or growth hormone concentrations for the time periods at which they were measured. CB154 treatment produced numerical, but not statistically significant, 38% reductions in interleukin 2 production (6.31 +/- 1.8 vs 3.91 +/- 1.47 units/ml). Lymphocyte proliferative responses to the mitogen concanavalin A and interleukin 2 production decreased 65 and 75% (P less than 0.05), respectively, 2 hr subsequent to ACTH administration when compared with control animals. Hence, under the conditions of this study, only a modest association between lowered plasma prolactin concentrations and basal cortisol concentrations was evident. The data suggest the absence of dopamine regulation of basal plasma ACTH in pigs and provide evidence for a rapidly occurring inhibitory effect of ACTH administration on specific lymphocyte activities.     

Evaluation of prostaglandin E1 for prevention of respiratory failure in high risk trauma patients: A prospective clinical trial and correlation with plasma suppressive factors for neutrophil activation

A group of 48 critically injured patients were entered into a prospective, double-blind, placebo-controlled trial to evaluate the efficacy of early infusion of PGE1 for reducing the incidence of severe respiratory failure and mortality. Secondary assessments examined the effects of the PGE1 infusion on plasma mediated suppression of PMN superoxide production and loss of PMN granule enzyme content. The incidence of severe respiratory failure was lower in the PGE1 group--13% versus 32%, but this did not reach significance. The overall morality was equivalent between the two groups--26% (PGE1) versus 28% (placebo). The suppressive activity of the patient plasma was assayed by measurement of normal PMN superoxide production relative to normal control plasma (ratio P:C). The baseline ratio P:C was 62 +/- 5% in the PGE1 group versus 60 +/- 5% in the placebo group. The day 1 plasma samples showed significant reversal of plasma suppressive activity in the PGE1 group--ratio P:C 88 +/- 5% versus 67 +/- 5% in the placebo group (P less than 0.02). In patients who received the full 7 days of infusion, the plasma suppressive activity remained significantly diminished in the PGE1 group--ratio P:C 77 +/- 4% versus 61 +/- 5% (P less than 0.04). The baseline lysozyme content of patient PMN's relative to that of normal control PMNs (ratio P:C) was 119 +/- 14% in the PGE1 group. A significant loss of lysozyme content was observed in the PGE1 group on day 1 of the infusion--ratio P:C 79 +/- 8% (P less than 0.03), and was associated with a reduction in the plasma suppressive activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diuretic effects on renal brush border membrane transport and metabolism

Previous studies have indicated that the thiazide diuretics exert effects on proximal electrolyte transport. To determine whether the locus of these effects is at the brush border membrane (BBM) and if renal metabolism is affected, adult female Sprague-Dawley rats were acutely treated with either 1 mg/kg metolazone, 20 mg/kg chlorothiazide followed by a 20 mg/kg/hr maintenance infusion, 10 mg/kg acetazolamide followed by a 10 mg/kg/hr maintenance infusion, or the vehicles only. Administration of these agents resulted in an approximately tenfold increase in sodium excretion. Neither urinary phosphate nor inulin excretion changed significantly in any group. Sodium dependent BBM vesicle phosphate transport was examined at 0.15, 0.5, and 1 and 120 minute incubation periods in the diuretic treated groups and their respective control groups. Decreased uptake was seen in all pre-equilibrium time points in rats treated with metolazone: 0.15 minutes: 221 +/- 24 pmoles/mg protein (pmol/mg prot) in control rats versus (vs) 185 +/- 23 pmoles/mg prot in metolazone-treated animals (P less than .05) ; 0.5 minutes: 463 +/- 54 vs 369 +/- 49 pmol/mg prot (P less than .005); 1 minute: 549 +/- 74 vs 460 +/- 61 pmol/mg prot (P less than .05); no significant difference in phosphate transport was noted at the two hour equilibrium time point. No significant differences in sodium dependent phosphate transport existed between chlorothiazide or acetazolamide treated rats and control animals. Substrate-stimulated renal gluconeogenesis did not differ between metolazone treated and control animals. We therefore conclude that metolazone inhibits phosphate transport through an effect on the BBM and does not affect renal gluconeogenesis in the rat.     

Effect of changes in sodium intake on atrial natriuretic factor (ANF) and peptides derived from the N terminus of the ANF prohormone in the rat.

The purpose of the present study was to determine whether variations in salt intake would alter the plasma concentrations of atrial natriuretic factor and the N-terminal atrial natriuretic factor prohormone peptides proANF 1-98 and proANF 31-67. Two groups of rats were placed on different salt intakes for 1 week. The low salt group of rats was fed a diet providing less than 0.1 mM NaCl/day and given deionized water to drink. The normal salt group of rats was fed regular rat chow with deionized water to drink, providing them with approximately 2 mM NaCl/day. Plasma atrial natriuretic factor was 204 +/- 60 pg/ml (mean +/- SE) in normal salt rats and was significantly lower in the low salt group (44 +/- 13 pg/ml, P less than 0.01). ProANF 1-98 was also significantly higher in the normal salt group (635 +/- 47 pg/ml) compared with the low salt group (353 +/- 33 pg/ml, P less than 0.01). ProANF 31-67 was 123 +/- 21 pg/ml in the normal salt group and 59 +/- 12 pg/ml in the low salt group (P less than 0.05). Plasma renin activity in ng angiotensin l/ml/hr averaged 1.80 +/- 0.15 in the normal salt group of rats and was significantly higher in the low salt group of rats (5.66 +/- 1.07, P less than 0.05). These results suggest that atrial natriuretic factor and the atrial natriuretic factor prohormones may play a role in the physiological adjustments to low salt intake.     

Similar bioavailability and lymphatic transport of benzo(a)pyrene when administered to rats in different amounts of dietary fat

This study assessed the effect of concomitant lipid absorption on the bioavailability and lymphatic transport of benzo(a)pyrene (BP), a carcinogenic polycyclic aromatic hydrocarbon (PAH). Conscious, male Sprague-Dawley rats, equipped with biliary and mesenteric lymphatic catheters received intraduodenally a dose of 0.4 mumoles 3H-labeled BP completely dissolved in either 50 mumoles or 500 mumoles of olive oil. Diversion of mesenteric lymph allowed biliary and urinary excretion of 3H to be used as an indirect measurement of relative 3H portal transport. Total radiolabel recovered in a 24-hr period in each group was 20.0 +/- 2.6% of the 3H dose given in 50 mumoles of oil, and 17.0 +/- 1.0% of the 3H dose administered in 500 mumoles of oil. In animals receiving the low-fat test meal, 79.4 +/- 1.4% of the recovered radiolabel was found in bile; the corresponding value for the high fat dose was 78.5 +/- 2.6%. Thus a tenfold variation in the mass of the carrier vehicle (triglyceride oil) did not significantly effect the disposition of BP, and portal, not lymphatic transport, was the major route of post-absorptive transport. Although the chylomicrons produced from both fat doses were initially contaminated with BP, within 1-1.5 hr the radioactivity in lymph began to drop such that by 3 hr in the animals fed high fat, the chylomicrons were essentially free of BP. These results show that the rat enterocyte quickly adapts to PAH-contaminated dietary fat, even during the assimilation of a single dose of fat. Presumably, during the post-absorptive synthesis of chylomicrons from pre-chylomicrons, BP is metabolized and removed from the triglyceride oil droplets.     

Changes in LPLa and reverse cholesterol transport variables during 24-h postexercise period

We investigated the time course of exercise-induced lipoprotein lipase activity (LPLa) and reverse cholesterol transport (RCT) during the 24-h postexercise period. Subjects were 10 sedentary normolipidemic males [NTG; fasting triglyceride (TG) = 89.1 +/- 8.6 mg/dl] and 6 hyperlipidemic males (HTG; fasting TG = 296.8 +/- 64.0 mg/dl). Each subject performed a control trial (no exercise) and 4 exercise trials. In the exercise trials, a subject jogged on a treadmill at 60% of his maximal O(2) consumption for 1 h. Pre- and postheparin blood samples were taken before exercise (baseline) and at 4, 8, 12, and 24 h after exercise. There was no group difference in LPLa (P > 0.05) over the time points. When the LPLa data from the two groups were combined, LPLa at 24 h after exercise was higher than baseline or at 4, 8, 12 h after exercise (P < 0.05). Plasma TG and lecithin-cholesterol acyltransferase activity (LCATa) were higher in HTG than in NTG, and the total high-density lipoprotein-cholesterol (HDL(tot)-Chol) was lower in HTG than in NTG (P < 0.05). HDL(2)-Chol, LCATa, and cholesterol ester transfer protein activity did not differ during the 24-h postexercise period (P > 0.05). These results suggest that LPLa is still increasing 24 h after an acute aerobic exercise and that the magnitude of the increase in exercise-induced LPLa in HTG was similar to that in NTG. Furthermore, in the sedentary population with or without HTG, the variables related to RCT do not change during the 24-h period after exercise.     

Metabolic and hormonal responses to prolonged physical exercise in dogs after a single fat-enriched meal

Metabolic and hormonal responses to prolonged treadmill exercise in dogs fed a fat-enriched meal 4 h prior to the exercise were compared to those measured 4 h after a mixed meal or in the postabsorptive state. Ingestion of the fat-enriched meal caused significant elevations in the resting values of plasma triglyceride (TG), free fatty acid (FFA), and glycerol concentrations. A reduction of the plasma TG concentration (from 1.6 +/- 0.2 to 1.1 +/- 0.10 mmol X l-1, P less than 0.005) occurred only in dogs exercising after the fat-enriched meal. No significant changes in this variable were noted in dogs fed a mixed meal, whilst in the postabsorptive state exercise caused an increase in the plasma TG level (from 0.42 +/- 0.03 to 0.99 +/- 0.11 mmol X l-1, P less than 0.01). The exercise-induced elevations in plasma FFA and glycerol concentrations were the highest in the dogs given the fat-enriched meal. Plasma glycerol during exercise correlated with the initial values of circulating TG (r = 0.73). The plasma FFA-glycerol ratio, at the end of exercise was lowest in the dogs taking the fat-enriched meal (1.39 +/- 0.19), suggesting an increased utilization of FFA in comparison with that in the postabsorptive state (3.27 +/- 0.37) or after a mixed meal (2.88 +/- 0.55). Basal serum insulin (IRI) concentrations were similarly enhanced in dogs fed fat-enriched and mixed meals, and they were reduced to control values within 60 min of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lipoproteins status in professional football players after period of vacation and one month after a new intensive training program

Plasmatic lipoproteins were evaluated in a group of 11 professional football-players after a 3-week rest, and one month later, after an intensive training (characterized by a succession of aerobic and anaerobic efforts), for engaging a new competition. At day 0, total cholesterol (TC = 4.4 +/- .04 mmol/l), triglycerides (TG = .6 +/- .04 mmol/l), and LDL-TC (2.54 +/- .18 mmol/l) were significantly decreased versus sex and age matched sedentary subjects (TC = 5.13 +/- .2 mmol/l, P less than .02; TG = .99 +/- . mmol/l, P less than .01; LDL-CT = 3.26 +/- .2 mmol/l, P less than .02). HDL-TC was increased (1.50 +/- .06 vs 1.30 +/- .05 mmol/l, P less than .05). The apoprotein A1 (apoA1) was higher in football-players (1.5 +/- .06 vs 1.16 g/l, P less than .001), while the apoprotein B (apoB) was lower (.6 +/- .03 vs .88 +/- .04 g/l, P less than .001). Even after 3 weeks of rest, the football-players lipoproteins were still identical to aerobic elite-athletes. At day +30, after a daily training involving 2 anaerobic sequences, the maximal aerobic capacity was increased by 21%, without any change in nutritional, plasmatic and hepatic status. Weight was diminished (-0.8 kg, P less than 0.05). TC (4.14 +/- .2 mmol/l), TG less than .64 +/- .08 mmol/l), LDL-TC (3.37 +/- .17 mmol/l), apo B (.64 +/- .05 g/l) were unchanged. HDL-CT fell to controls values while apoA1 increased (1.66 +/- .06 mmol/l, P less than .001). Thus, HDL-CT/apoA1 ratio (indicating the TC content of HDL) was decreased, whereas apoB/apoA1 ratio was unchanged. The decrease of TC content of HDL was not related to dietary change nor to weight decrease. As TG were stable, the lipoprotein lipase activity could not be modified.(ABSTRACT TRUNCATED AT 250 WORDS)