Urinary kallikrein excretion in a spontaneously hypertensive strain of rats.

Concentration and 24-hr excretion of urinary kallikrein in spontaneous hypertensive Wistar strain rats of both sexes obtained by selected inbreeding (25th generation) are significantly decreased as compared with the excretion in normotensive inbred rats (24th generation) descending from common ancestors. Apparently in these hypertensive rats there is an abnormal capacity of the kidneys to produce or release kallikrein, but more studies will be necessary to correlate this findings with blood pressure increase.     

Effect of treatment on longevity in spontaneously hypertensive rats.

Continuous control of the pressure of spontaneously hypertensive rats at systolic levels of 90-100 mm Hg with antihypertensive agents significantly prolonged their life span. The mean survival time in control animals was 73 weeks as compared to 96 weeks in treated SHR (P less than .0005) with 11% of the latter surviving to approximately 3 yr of age. Cardiovascular lesions were limited almost exclusively to the control rats. The general health, body weight and reproductive functions of the experimental animals remained normal throughout the drug treatment. These results indicate that by preventing the rise in blood pressure and consequent cardiovascular complications the life span of the SHR may be prolonged to that of the normal albino rat.     

Cadmium tolerance plasticity in Rhizobium leguminosarum bv. viciae: glutathione as a detoxifying agent

Rhizobium leguminosarum bv. viciae strains expressing different degrees of tolerance to metal stress were used in this work to study the basic mechanisms underlying heavy metal tolerance. We used various parameters to evaluate this response. The strains' growth responses under different Cd2+ concentrations were determined and we reported variation in Cd2+ tolerance. Total soluble protein content decreased drastically, revealing the toxic effects that intracellular Cd2+ imposes on cellular metabolism, but this decrease in protein content was particularly evident in sensitive and moderately tolerant strains. Tolerant strains presented the highest intracellular and wall-bound Cd2+ concentrations. Cd2+ induced increases in the expression of some specific proteins, which were identical in all tolerant strains. Glutathione levels remained unaltered in the sensitive strain and increased significantly in tolerant and moderately tolerant strains, suggesting the importance of glutathione in coping with metal stress. This work suggests that efflux mechanisms may not be the only system responsible for dealing with heavy metal tolerance. A clear correlation between glutathione levels and Cd2+ tolerance is reported, thus adding a novel aspect in bacteria protection against heavy metal deleterious effects.     

Effect of increased bromide intake on iodine excretion in rats

The time course of iodine excretion in adult male rats substantially differs from bromine excretion. Bromine is excreted at a single rate, whereas iodine evinces two excretion rates. Even a strong increase in bromide intake in experimental animals failed to affect the rate of iodine excretion but it lowered the fraction of iodine accumulated increase in bromide intake in experimental animals failed to affect the rate of iodine excretion but it lowered the fraction of iodine accumulated in the thyroid gland by 20% probably by affecting the transport of iodide into the thyroid gland.     

Effect of androsole acetate on blood pressure of stress-sensitive hypertensive rats.

The basal and stress-induced blood pressure was found to decrease in rats with inherited stress sensitive hypertension (SSHR) followed by androzole acetate administration orally (30 mg/kg body weight) for eight days. The basal levels of arterial blood pressure was decreased by 17.5% and that of stress-induced animals--by 19%.     

Effect of norepinephrine and vasopressin on renal kallikrein excretion in rats

The purpose of this study was to investigate the effect of norepinephrine and vasopressin on urinary kallikrein excretion in the rat. Two studies were undertaken: (a) acute experiments in which the rats were infused with 30% dextrose in water with the addition of norepinephrine or vasopressin, (b) chronic experiments in which the drugs were infused during seven days through an osmotic minipump. In acute experiments, urinary kallikrein excretion increased without modification in urinary flow and glomerular filtration rate. In chronic experiments, urinary kallikrein excretion was not modified in norepinephrine-treated rats and decreased in vasopressin-infused animals. This decrease followed the modifications of the urine flow. In chronic experiments the dextrose infusion increased urinary kallikrein excretion. In all the groups studied a positive correlation between urine flow and urinary kallikrein excretion was observed. It is concluded that norepinephrine and vasopressin are important stimulators of the urinary kallikrein excretion only in those circumstances where it is necessary to eliminate an excess of water.     

Effect of hyperosmotic solutions on salt excretion and thirst in rats

We investigated urinary changes and thirst induced by infusion of hyperosmotic solutions in freely moving rats. Intracarotid infusions of 0.3 M NaCl (4 ml/20 min, split between both internal carotid arteries) caused a larger increase in excretion of Na(+) and K(+) than intravenous infusions, indicating that cephalic sensors were involved in the response to intracarotid infusions. Intravenous and intracarotid infusions of hyperosmotic glycerol or urea (300 mM in 150 mM NaCl) had little or no effect, suggesting the sensors were outside the blood-brain barrier (BBB). Intracarotid infusion of hypertonic mannitol (300 mM in 150 mM NaCl) was more effective than intravenous infusion, suggesting that cell volume rather than Na(+) concentration of the blood was critical. Similarly, intracarotid infusion (2 ml/20 min, split between both sides), but not intravenous infusion of hypertonic NaCl or mannitol caused thirst. Hyperosmotic glycerol, infused intravenously or into the carotid arteries, did not cause thirst. We conclude that both thirst and electrolyte excretion depend on a cell volume sensor that is located in the head, but outside the BBB.     

Decrease in urinary excretion of active kallikrein in conscious young and adult spontaneously hypertensive rats

Urinary excretion of active kallikrein was determined every day (amidolytic assay) in 6 male Okamoto-Aoki spontaneously hypertensive rats (SHR) and 6 male normotensive Wistar-Kyoto rats (WKY) from ages 4 to 7 weeks and from 12 to 15 weeks. The rats were housed in individual metabolic cages and were allowed free access to food having normal sodium content and to tap water. Urinary kallikrein excretion was lower in 4-week-old SHR than in age-matched WKY (7.8 +/- 1.4 vs. 15.5 +/- 2.3 nkat/24 h respectively, P less than 0.01) at a moment when systolic blood pressure (BP) in SHR was already higher than in WKY. The slope of the increase in active kallikrein excretion from week 4 to 7 was not different for SHR and WKY (6.34 +/- 1.05 vs. 7.50 +/- 1.02 nkat/24 h-1 . wk-1 respectively). In contrast, from week 12 to 15, this slope was not significant for SHR (1.67 +/- 2.55 nkat/24 h-1 . wk-1) while it remained positive in WKY (7.36 +/- 3,44 nkat/24 h-1 . wk-1). In both SHR and WKY, urinary kallikrein excretion was directly related to BP from week 4 to 7 but the slope of the regression line was less for SHR than for WKY (0.19 +/- 0.05 vs. 0.48 +/- 0.12 nkat/24 h-1 . mm Hg respectively). From ages 12 to 15 weeks, kallikrein excretion was still related to pressure in WKY (y = 1.92 x - 180.8; r = 0.93) but not in SHR (y = 0.71 x - 81.48; r = 0.52).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of exenatide on glycemia and renal water and ion excretion differ in frogs and rats

The aim of this study was to compare the effects of exenatide, a glucagon-like peptide-1 (GLP-1) mimetic, on glucose and water–salt homeostasis in animals with different levels of renal proximal tubular reabsorption, rats (Rattus norvegicus) and frogs (Rana temporaria). Following the glucose tolerance test, in rats exenatide promoted fast recovery of normoglycemia, whereas in frogs it delayed this process. In water-loaded rats, exenatide augmented solute-free water clearance and enhanced natriuresis in furosemide-treated animals. In frogs, exenatide did not alter the urinary flow rate, urinary sodium excretion and solute-free water clearance under water diuresis and furosemide treatment. It is suggested that the involvement of GLP-1 in regulation of water–salt homeostasis in mammals was preceded by a key evolutionary transformation, the increase in the glomerular filtration rate and proximal tubular reabsorption.     

Effect of 3-methylcholanthrene on the biliary excretion of bromsulphthalein and eosine in newborn rats.

The biliary excretion rates of bromsulphthalein (BSP), bromsulphthalein-glutathione conjugate (BSP-GSH) and eosine have been studied in 3-methylcholanthrene (3-MC)-pretreated (100 mg/kg i.p.) and control rats aged 10 days. Liver weight was invariably increased after 3-MC treatment, associated with enhanced biliary excretion of total BSP. The increase in the biliary excretion of total BSP was due solely to the increased excretion of BSP-GSH. Following 3-MC pretreatment, BSP-GSH and eosine appeared in the bile in the same amount as in the control rats after i.v. administration of BSP-GSH and eosine. Pretreatment with 3-MC increased the ratio of BSP-GSH to BSP in the liver and bile. Our results suggest that the increased biliary excretion of total BSP following 3-MC treatment was due to an enhanced conjugation of BSP with GSH.     

Effect of diphenylhydantoin on blood pressure of spontaneously hypertensive rats

Diphenylhydantoin (DPH) has been shown to elicit direct peripheral vasodilatory effects in anaesthetised animals. Since spontaneously hypertensive (SH) rats exhibit many features similar to human essential hypertension, the effect of DPH on blood pressure of these rats was studied. DPH given orally for 5 days elicited dose-dependent fall in systolic blood pressure in conscious SH rats. In addition, repeated administrations of DPH increased the noradrenaline concentration in the hypothalamus. These results suggest that the central noradrenergic mechanisms might be involved in the hypotensive action of DPH in SH rats, probably at the supramedullary level.