Determination of optimum fat intake

In a 14-day experiment, adult rats weighting 250-260 g were given ad libitum diets with a constant protein content [casein - 10 %] and a mounting fat content [margarine - 0, 10, 20, 30 and 40 % - added at the expense of carbohydrates]. The growth parameters of protein biological value - PER and NPR - were determined and together with weight increments in correlation to protein an fat intake [a linear correlation] they were used on the basis of their regression equations to calculate the reciprocal relationships of fat and protein intake [for equality y]. By substituting the optimum protein intake [43.3 g/14 days - according to NPU], the optimum fat intake for adult rats was found to correspond to dietary fat concentrations of 9.72 % [y = weight increments], 12,82 % [y = PER] and 11.83 % [y = NPR]. These results wee verified in a biological experiment in which adult animals, for 14 days, were given a limited amount [31 g/animal per day] of diets containing 10 % protein [casein] an d9, 10, 11, 12, and 13 % fat [margarine - at the expense of carbohydrates] with the aim of studying the effect of a mounting fat intake on optimum protein intake [43.4 g/14 days]. The correctness of the mathematical method for determining the optimum fat intake was verified by a biological method [the optimum net protein utilization , NPU, which is highest in diets containing 11 % fats, i.e. 22.5 % of the total energy value of the diet]. It was also found that this method, both along and in conjunction with other methods [especially the one using the NPR parameter], was suitable for the determination of optimum nutrient values.     

Effect of underfeeding on the inhibition of gonadotrophin secretion by testosterone propionate in rats.

Single (0 . 25 mg/100 g body wt) or multiple (5 x 20 microgram/100 g) injections of testosterone propionate were given to castrated male rats fed normally or restricted to a 50% intake. Serum FSH and LH levels were higher in the underfed rats and the effectiveness of testosterone propionate in suppressing serum levels of gonadotrophins was increased by underfeeding.     

Effect of prolonged high salt intake on atrial natriuretic factor's kinetics in rats

Plasma atrial natriuretic factor (ANF) paradoxically decreases after 5 weeks (but not after 3 weeks) of 8% NaCl intake in normotensive rats. As this phenomenon remains unaccounted for by changes in ANF production, we studied the disappearance of [125I]ANF(99-126) from the circulation as an alternative explanation of plasma ANF decline. Following 5 weeks (but not 3 weeks) of an 8% NaCl diet, plasma concentrations of [125I]ANF were significantly decreased and metabolic clearance rate and volume of distribution were increased compared to control rats fed a 0.8% NaCl diet. By studying [125I]ANF tissue uptake we noted significantly greater peptide uptake after 5 weeks (but not after 3 weeks) of high salt consumption in several tissues. We hypothesize that prolonged (at least 5 weeks) 8% NaCl ingestion increases the density and/or affinity of ANF binding sites. These changes may be responsible for the previously observed decline in plasma ANF concentrations after a prolonged high salt intake.     

Effects of gonadal hormones on eating and body weight in mongolian gerbils (Meriones unguiculatus)

The effects of gonadal steroids on food intake and body weight were studied in Mongolian gerbils. Orchiectomy of adult male gerbils caused significant increases in body weight but had no detectable effect on food intake. Treatment with testosterone propionate or 5α-dihydrotestosterone propionate (100 μg/day) had no effect on food intake or body weight of orchiectomized males, but withdrawal of exogenous androgen treatment had the same effect as orchiectomy, increased body weight with no increase in food intake. Treatment with estradiol benzoate (EB; 2 μg/day) increased food intake and body weight of ovariectomized gerbils, but progesterone (1 mg/day) had no effect on these measures when given by itself. However, when progesterone was given concurrently with EB it synergized with the estrogen and further increased eating and body weight. These results are contrasted with previous work in other mammalian species.     

Water and sodium balance in the estuarine diamondback terrapin (Malaclemys)

Summary Total body water decreased significantly in terrapins exposed to sea water (SW). Although the intracellular fluid decreased somewhat upon SW exposure, the decline in extracellular fluid was almost twice as great. Under conditions of voluntary drinking after salt loading, terrapins substantially increased the volume of the extracellular fluid while maintaining the intracellular fluid near the freshwater (FW) control levels. FW terrapins were consistently heavier than animals of the same plastron length exposed to SW. Thus expression of body fluid volumes as ml/cm plastron length rather than as % body weight is necessary to correct for the loss of total body water with progressive dehydration. Fasted terrapins in SW lost weight at 0.32% weight/day, whereas the rate in FW was 0.21%/day. Water influx and efflux in SW were 0.17 and 0.16 ml/100 g·h respectively. When the efflux was increased by the calculated value for unmeasured respiratory loss, it exceeded the influex by 0.01 ml/100 g·h. Consequently the net water loss determined with radiotracers (equivalent to 0.24% weight/day) was similar to the difference between the weight losses in SW and FW (0.11%/day). Partitioning studies indicated that the majority of water exchange between the terrapin and SW occurs through the integument. Terrapins in SW underwent a concentration of the body fluids, most of which can be attributed to water loss, not electrolyte gain. The rates of Na influx and efflux were quite low (usually ranging from 6–10 moles/100 g·h). In two terrapins the injection of NaCl loads resulted in eight- to 19-fold increases in Na efflux. The uptake of Na from SW occurred orally. The skin was virtually impermeable to Na. The salt gland and possibly the cloaca were the major routes of Na efflux. The injection of NaCl loads resulted in an increase in cephalic Na excretion from a mean of 3.2 moles/100 g·h to 32.5 moles/100 g·h. Terrapins in SW exhibited a significant increase in bladder urine [K] over the FW controls. There was a direct relationship between plasma [Na], urine [K], and lachrymal salt gland Na–K ATPase content. In comparing SW terrapins with FW painted turtles (Chrysemys) exposed to SW radiotracer studies demonstrated a similarity in Na influx, but there was at least a four-fold increase in water exchange in the painted turtle. It seems likely that the skins of many aquatic reptiles (marine, estuarine and FW) are impermeable to Na but differ markedly in water permeability.     

Anti-fertility effects of embelin in female Sprague-Dawley rats may be due to suppression of ovarian function

Effects of embelin on oestrous cycle, plasma levels of progesterone and oestradiol, and in vitro production of oestradiol and progesterone by mixed ovarian cells was studied. Forty adult (4 months old) regularly cycling female Sprague-Dawley rats were divided into four groups of 10 rats each. Groups I and II (controls) were given 1 ml/kg body weight of physiological saline or corn oil (vehicle). Groups III and IV received 10 mg/kg and 20 mg/kg body weight embelin in corn oil, respectively. Emberlin disrupted the oestrous cycles in Groups III and IV animals, and there was a significant depression in plasma oestradiol (p <0.05) and progesterone (p <0.02) at both 10 and 20 mg/kg body weights, respectively. Isolated mixed ovarian cells from embelin treated rats produced significantly less progesterone and estradiol than controls in vitro. It is concluded that embelin probably interferes with reproductive functions in female rats by suppressing ovarian production of sex steroid hormones.     

NaCl intake and preference threshold of spontaneously hypertensive rats.

Both male and female spontaneously hypertensive (SH) rats have an appetite for NaCl solution. The appetite is present when a choice is offered between distilled water and either isotonic or hypertonic (0.25 M) NaCl solution to drink. Total fluid intake (water plus NaCl solution) was greater for SH rats than for controls while food intakes (g/100 g body wt/day) of SH rats were not different from controls. Mean body weight of SH rats was always less than that of controls. The appetite for NaCl solution was accompanied by a significant reduction in preference (detection) threshold. SH rats could detect the difference between distilled water and NaCl solution when the concentration of the latter was 12 mEq/liter compared to a control threshold of 30 mEq/liter. The NaCl appetite and reduced NaCl preference threshold induced by spontaneous hypertension is in marked contrast to the NaCl aversion induced by other types of experimentally induced hypertension in rats. The mechanism or mechanisms responsible for these differences remain for further study.     

Distribution of Tocotrienols in Rats Fed a Rice Bran Tocotrienol Concentrate

To examine the distribution of rice bran tocotrienol (T3), we gave rice bran T3 to rats after considering an acceptable daily intake of vitamin E for humans. Male SD rats (5 weeks of age) were fed for 3 weeks on a commercial diet containing 6.4 mg of vitamin E per 100 g wt and additively received vitamin E or the vehicle (vitamin E-free corn oil) by oral intubation. The animals were randomly divided into 4 groups depending on the type of test diet: control (vehicle), non-T3 (no T3 + 4.3 mg of tocopherol (TOC)/kg body weight (b.w.)/day), low-T3 (0.8 mg T3 + 3.5 mg TOC/kg b.w./day), and high-T3 (3.2 mg T3 + 1.1 mg TOC/kg b.w./day). The control rats and rats in the non-T3, low-T3, and high-T3 groups took 4.3 and 8.6 mg of vitamin E/kg b.w./day, respectively. Rice bran γ-T3 was significantly distributed to the adipose tissue and increased from 1.1 to 10.2 nmol/g of adipose tissue according to the rice bran T3 intake.     

Distribution of tocotrienols in rats fed a rice bran tocotrienol concentrate

To examine the distribution of rice bran tocotrienol (T3), we gave rice bran T3 to rats after considering an acceptable daily intake of vitamin E for humans. Male SD rats (5 weeks of age) were fed for 3 weeks on a commercial diet containing 6.4 mg of vitamin E per 100 g wt and additively received vitamin E or the vehicle (vitamin E-free corn oil) by oral intubation. The animals were randomly divided into 4 groups depending on the type of test diet: control (vehicle), non-T3 (no T3 + 4.3 mg of tocopherol (TOC)/kg body weight (b.w.)/day), low-T3 (0.8 mg T3 + 3.5 mg TOC/kg b.w./day), and high-T3 (3.2 mg T3 + 1.1 mg TOC/kg b.w./day). The control rats and rats in the non-T3, low-T3, and high-T3 groups took 4.3 and 8.6 mg of vitamin E/kg b.w./day, respectively. Rice bran gamma-T3 was significantly distributed to the adipose tissue and increased from 1.1 to 10.2 nmol/g of adipose tissue according to the rice bran T3 intake.     

Immune suppression blocks sodium-sensitive hypertension following recovery from ischemic acute renal failure

The present study determined the effect of immune suppression with mycophenolate mofetil (MMF) on sodium-sensitive hypertension following recovery from ischemia reperfusion (I/R)-induced acute renal failure. Male Sprague-Dawley rats fed 0.4% NaCl chow were subjected to 40 min bilateral I/R or control sham surgery. After 35 days of recovery, when plasma creatinine levels had returned to normal, the rats were switched to 4.0% NaCl chow for 28 days and administered vehicle or MMF (20 mg.kg(-1).day(-1) ip). High-salt mean arterial pressure was significantly higher in I/R rats (144 +/- 16 mmHg) compared with vehicle-treated sham rats (122 +/- 2 mmHg). Treatment of I/R rats with MMF during the period of high salt intake prevented the salt-induced increase in arterial pressure (114 +/- 3 mmHg). Conscious creatinine clearance was lower in I/R rats (0.27 +/- 0.07 ml.min(-1).100 g body wt(-1)) compared with vehicle-treated sham rats (0.58 +/- 0.04 ml.min(-1).100 g body wt(-1)); MMF treatment prevented the decrease in creatinine clearance in I/R rats (0.64 +/- 0.07 ml.min(-1).100 g body wt(-1)). I/R injury also significantly increased glomerular tissue damage and increased the presence of ED-1 positive (macrophages) and S100A4 positive cells (fibroblasts) in the renal interstitium. The I/R rats treated with MMF exhibited a significant reduction in infiltrating macrophages and fibroblasts and decreased histological damage. The present data indicate that infiltrating immune cells mediate or participate in the development of sodium-sensitive hypertension and renal damage in rats apparently recovered from renal I/R injury.     

Effect of salt loading on the body water compartments in rats of different ages

In acute experiments on anaesthetized rats from three age groups (15-20, 25-30 days of postnatal life, adult ones), studies have been made on water basins of the organism after peroral injection of hypertonic (2.5-5%) solutions of NaCl (5 and 10 ml per 100 g of the body weight). It was demonstrated that during ontogenesis, total content of water decreases mainly at the expense of extracellular fluid. Infusion of saline solutions into the stomach of rats decreases fluid content in all water basins, especially in the interstitial one. The level of changes depends on the volume of the injected solution and, to a greater extent, on the concentration of the latter and the age of animals. The described response is due to osmotic transport of water into the alimentary tract, as suggested by the decrease of water content in this tract. The role of the digestive tract in osmotic and volume regulation during peroral salt loading is discussed.     

Oestrogenic sensitivity of rat uterine secretion.

Ovariectomized adult rats with closed uteri were treated for 7 days with different oral and s..c. doses of oestradiol, oestrone, oestriol and ethinyl oestradiol. All treatments elicited the production of uterine fluid and the potencies of oestrogens were related to the amount of fluid secreted. Ethinyl oestradiol and oestradiol displayed similar activity when given s.c. A daily dose of 0-003 mg oestradiol/kg resulted in about 700 mg fluid. Oestrone was 3-10 times and oestriol about 100 times less active. Orally, ethinyl oestradiol was the most potent substance and 700 mg secretion was obtained with a dose of 0-03 mg/kg daily. Oestradiol was about 30 times, oestrone about 100 times and oestriol 50 times less active than ethinyl oestradiol by this route. The viscosity of the secretion was unaffected, remaining between 1-6 and 2-4 cP. The pH of the fluid did not change, but that of the uterine lumen diminished slightly. These effects of oestrogens were associated with an increase in the weight of the empty uterus and a decrease in body weight.     

Effect of varying concentrations of linoleic acid on alpha-adrenoceptor responses in spontaneously hypertensive rats

The effect of increased intake of linoleic acid on the alpha-adrenergic system was assessed by safflower oil supplementation to spontaneously hypertensive rats. Linoleic acid-enriched intake at 5%, 15% and 30% by weight of total food intake for 12 wk was associated with a reduction in resting arterial blood pressure, while heart rate and heart to body weight ratios were similar to control group values. A dose-response analysis to norepinephrine bitartrate administered intravenously indicated a significant reduction in the vascular reactivity to this alpha-adrenergic agonist in all groups given linoleic acid. Direct assessment of alpha-adrenoceptor number (Bmax) and affinity (KD) in cardiac sarcolemma with [3H]-prazosin indicated that receptor binding properties were not affected by linoleic acid intake. Our results suggest that short-term linoleic acid supplementation in the established hypertensive state may lower blood pressure through effects upon alpha-adrenergic reactivity in vascular tissue, without associated effects in cardiac tissue.     

Potentiation of carbon tetrachloride hepatotoxicity by chlordecone: Dose-response relationships and increased covalent binding in vivo

Chlordecone greatly potentiates carbon tetrachloride (CC1₄) hepatotoxicity. In order to quantitate the degree of this potentiation, the effects of a range of doses of CC1₄ on two microsomal enzymatic functions and liver enzyme release were examined in chlordecone-treated and control rats. Male Sprague-Dawley rats were pretreated with 15 mg chlordecone per kilogram body weight (BW) intragastrically or with vehicle. After 48 hours, 0 to 250 μ1 CC1₄ per 100 g body weight were given intraperitoneally (IP), and the rats were killed 24 hours later. Chlordecone treatment produced approximately a 17-fold potentiation of the CC1₄ dependent loss of cytochrome P-450 and glucose-6-phosphatase activity, so that a dose of 6 μ1 CC1₄ per 100 g body weight in the chlordecone-treated animals resulted in a similar amount of damage as observed with 100 μ1 CC1₄ per 100 g body weight in controls. A similar potentiation by chlordecone was seen with CC1₄- induced increases in serum glutamic-oxaloacetic transaminase (SGOT) levels. Chlordecone treatment also increased hepatic cytochrome P-450 levels by 67% and resulted in an increase in the covalent binding of [14-C]-CC1₄-derived metabolites to microsomal protein and lipid in vivo.     

Effect of Arnica montana tincture on some hydrolytic enzyme activities of rat liver in experimental toxic hepatitis]

Effects of tinctura arnica on arginase, adenosine triphosphatase, glucose-6-phosphatase and 5'-nucleotidase activities of rats liver in case of experimental toxic hepatitis have been studied. Toxic hepatitis was caused by 2 times interstomach administration of 0.25 ml oil solution of carbon tetrachloride per 100 g of animal weight. 20 mkl/100 g of tinctura arnica was administered every day per os for 14 days. The enzyme activities have been investigated at 3, 7 and 17 days. A significant demention of a studied hydrolytic enzyme activities in rats liver at intoxication of the body by CCI4 has been shown. It has been established that tinctura arnica administered per os to intoxicated animals sped up the normalization of hydrolytic enzyme activities in rat liver.     

Thirst and salt appetite responses in young and old Brown Norway rats

Male Brown Norway rats aged 4 mo (young) and 20 mo (old) received a series of experimental challenges to body fluid homeostasis over approximately 3 mo. Water was available for drinking in some tests, and both water and 0.3 M NaCl were available in others. The series included three episodes of extracellular fluid depletion (i.e., furosemide + 20 h of sodium restriction), two tests involving intracellular fluid depletion (i.e., hypertonic saline: 1 or 2 M NaCl at 2 ml/kg body wt sc), one test involving overnight food and fluid restriction, and testing with captopril adulteration of the drinking water (0.1 mg/ml) for several days. Old rats were significantly heavier than young rats throughout testing. Old rats drank less water and 0.3 M NaCl after sodium deprivation than young rats, in terms of absolute and body weight-adjusted intakes. Old rats drank only half as much water as young rats in response to subcutaneous hypertonic NaCl when intakes were adjusted for body weight. Old rats drank less 0.3 M NaCl than young rats after overnight food and fluid restriction when intakes were adjusted for body weight. In response to captopril adulteration of the drinking water, young rats significantly increased daily ingestion of 0.3 M NaCl when it was available as an alternative to water and significantly increased daily water intakes when only water was available, in terms of absolute and body weight-adjusted intakes. Old rats had no response to captopril treatment. These results add important new information to previous reports that aging rats have diminished thirst and near-absent salt appetite responses to regulatory challenges.     

Adaptation capacity of Boer goats to saline drinking water

Due to global climatic changes, water and soil salinization is an increasing worldwide phenomenon, thus creating new threats for farm animal production. The present study was designed to investigate the adaptation capacity of goats towards sodium chloride (NaCl) in drinking water. Twelve non-pregnant Boer goats with an average body weight of 50.5 ± 9.0 kg were kept in individual pens. The study was conducted in four phases applying a two-choice preference test. In the control phase (phase 1) only fresh water was supplied in two containers. In phase 2, water with different salt concentrations (0.25%, 0.5%, 0.75%, 1.0%, 1.25% and 1.5%) was offered in one container and tap water in the other (sensitivity test). During the third phase (adaptation), goats were stepwise habituated to saline water by offering only saline water with different increasing concentrations (between 0% and 1.5% NaCl) in both containers. Subsequently, in phase 4 (sensitivity re-test) the same treatment as in phase 2 was repeated. Goats had ad libitum access to hay, water and a mineral licking block. Individual water and feed intake were recorded daily, while body weight and body condition score were measured every 2^nd week. Body weight was not affected by saline water intake, whereas dry matter intake and body condition scores decreased significantly during the experiment. Water intake was significantly (P<0.001) higher in phase 2 (sensitivity test) and phase 3 (adaptation), compared to phase 1 (control) and phase 4 (sensitivity re-test). Total sodium intake followed the same pattern. In phase 2, when goats had the choice between fresh and saline water for the first time they preferred higher salt concentrations and consumed significantly (P<0.001) higher amounts of saline water (75.4 ± 53.2 g/kg BW^0.82 per day) than in the re-test (40.4 ± 34.0 g/kg BW^0.82 per day) after the habituation period. Thus, salt discrimination rejection thresholds were lowered to 1.25% in phase 4 compared to 1.5% in phase 2. The results suggest that a stepwise adaptation to saline drinking water in goats is an effective method to habituate the animals to saline water intake when concentrations were below 1.5%. Goats reacted more sensitively to the salinity of drinking water after prolonged exposure to saline water indicating flexible regulation mechanisms depending on the total sodium balance of the animal.     

Effects of dexamethasone on lipid metabolism in rat organs

Injecting of dexamethasone (10 mg/kg body weight) for 8 days to rats decreased the body weight and feed intake by 29 and 50%, respectively. The increase in weights of liver, heart, kidneys and testes per 100 g body weight was 55, 37, 33 and 13%, respectively. Though, in general, the triglyceride content increased in all the organs, maximum increase (9-fold) was observed in the liver. The plasma showed elevated levels of triglycerides, cholesterol and phospholipids. In hepatic mitochondrial membranes, the content of protein, phospholipids and cholesterol decreased/g tissue. The percent 14C distribution, as a part of total incorporation in nonpolar lipids, of [14C]acetate into triglycerides of liver, kidneys and testes increased significantly. The increased turnover of phospholipids in liver and heart was mainly due to increased turnover of phosphatidyl choline (PC) and phosphatidyl ethanolamine in liver and PC in heart. Turnover of phospholipids of testes was not affected.     

High salt intake-induced changes in atrial natriuretic factor kinetics are mediated by clearance receptors.

We have reported a paradoxical plasma atrial natriuretic factor (ANF) decline following prolonged high salt intake that was attributed to an increased tissue uptake of circulating ANF, leading to its augmented distribution volume (Vas) and metabolic clearance rate (MCR) as compared with control rats on a standard diet. To explore this phenomenon further, we evaluated possible chronic salt-loading-induced changes in ANF clearance (C-ANF) receptors, which appear to play a major role in ANF removal from the circulation. We studied changes in plasma [125I]ANF(1-28) and its pharmacokinetics after preoccupation of C-ANF receptors by its specific ligand, C-ANF(4-23), in high-salt-treated rats and their controls. Following C-ANF(4-23) administration, we detected significantly higher circulating [125I]ANF levels throughout the study period (8 min) in high-salt-fed rats compared with the controls (280-470% vs 100-215% increase of basal values, P less than 0.05). C-ANF(4-23) infusion caused a significantly greater decrease of the metabolic clearance rate and distribution volume of [125I]ANF in high-salt-fed rats than in control animals (74 +/- 6% vs 41 +/- 6% and 75 +/- 4% vs 50 +/- 5% of basal values, respectively; P less than 0.05). These data suggest that a prolonged high salt diet may increase the availability of C-ANF receptors and, through this mechanism, may negatively modulate plasma ANF concentrations. C-ANF receptors may thus fulfill a regulatory function on circulating ANF during prolonged salt loading in rats.     

Genetic influence on saline consumption and salt hypertension as exhibited by the response of various rat strains and sub-strains.

Female rats of 2 Sprague-Dawley sub-strains and of the Wistar and Fischer 344 strains were sensitized to the hypertensogenic effect of excess salt by removal of 1 kidney and by being given 1% NaCl solution as their sole drinking fluid. One of the Sprague-Dawley sub-strains (SPD) and the Wistar (CFEP) rats developed progressive saline polydipsia of equivalent degree, blood pressure rose, and about half of the members became hypertensive during treatment. Rats of the other Sprague-Dawley strain (CFNP) also showed a progressive saline intake; but although they drank substantially less saline, the incidence of hypertension among them was increased by 50%. Animals of the Fischer 344 strain displayed neither saline polydipsia--the intake remaining relatively constant at a very low level throughout the experiment--nor hypertension. Salt hypertension appears to be affected by genetic factors in at least 2 ways, one of which regulates the quantity of salt ingested (salt appetite), while the other controls the susceptibility to salt excess or perhaps to hypertension per se. Fischer 344 rats have the ability to restrict the volume consumption of saline; their resistance to enforced high salt intake has yet to be established.