We found an experimental solution to the paradox when the reabsorption of solute-free water increases with a simultaneous increase in diuresis and saluresis in the rat kidney under the oxytocin action. Injection of oxytocin to rats (0.25 nmol/100 g of body weight) increases diuresis from 0.
View Article and Find Full Text PDFThe nonapeptides of neurohypophysis, vasotocin and mesotocin, detected in most vertebrates, are replaced by vasopressin and oxytocin in mammals. Using bioinformatics methods, we determined the spectrum of receptor subtypes for these hormones in mammals and their physiological effects in the kidneys of rats. A search for sequences similar to the vertebrate vasotocin receptor by proteomes and transcriptomas of nine mammalian species and the rat genome revealed three subtypes of vasopressin receptors (V1a, V1b, and V2) and one type of oxytocin receptors.
View Article and Find Full Text PDFThe human and animal osmoregulation system is aimed at stabilizing serum osmolality in order to maintain cell volume. It has been shown that the introduction of 5 mL water per 100 g of body weight into the stomach of rats decreases serum osmolality and the concentration of Na and Ca, but not K and Mg. The cascade system of osmotic homeostasis increases secretion of glucagon-like peptide-1 (GLP-1) and oxytocin, and decreases secretion of vasopressin, which reduces the osmotic permeability of collecting duct.
View Article and Find Full Text PDFIn rats, intramuscular injection of oxytocin (0.25 nmol/100 g body weight) increased sodium excretion from 19±5 to 120±11 μmol/min. A significant correlation (p<0.
View Article and Find Full Text PDFIn mammals, three subtypes of V-receptors have been identified in the kidney. The effects of vasopressin, a hormone synthesized in the hypothalamus, are triggered by three distinct receptor isoforms: V2, V1a, and V1b. Stimulation of V2-receptors regulates urine osmotic concentration by increasing sodium reabsorption in the thick ascending limb of the loop of Henle and enhancing osmotic permeability of the epithelium cells in the collecting duct.
View Article and Find Full Text PDFWe developed an approach for quantitative assay of injected vasopressin in urine samples by ELISA under conditions of physiological suppression of hormone secretion from the neurohypophysis into the blood. In experiments on unanesthetized rats, water load (5 ml/100 g body weight) almost completely blocked secretion of arginine-vasopressin. Injection of arginine-vasopressin in a dose of 0.
View Article and Find Full Text PDFAfter a water load in rats hyperhydration occurs and the secretion of oxytocin increases by the neurohypophysis. This increases the water diuresis, the water is quickly excreted by the kidney, and the recovery of osmotic homeostasis is accelerated.
View Article and Find Full Text PDFBlood concentration of glucagon-like peptide-1 (GLP-1) increased 5 min after per os administration of water, sodium chloride solution, or glucose solution. Changes in blood osmolality or blood glucose level did not stimulate GLP-1 release. A method of short-term increase in the gastric capacity in rats using an inflating balloon attached to the Foley catheter was developed in order to test the hypothesis that excitation of the upper gastrointestinal tract receptors is a primary signal for the GLP-1 secretion during oral intake of the substances.
View Article and Find Full Text PDFAn increase of total glucagon-like peptide-1 (GLP-1) concentration in the plasma in rats was revealed 5 min after oral, but not intraperitoneal administration of NaCl or Trizma HCl solutions. The increase in GLP-1 level was similar to that after oral glucose administration. After intraperitoneal administration of 2.
View Article and Find Full Text PDFRoss Fiziol Zh Im I M Sechenova
October 2016
In experiments with female Wistar rats it was shown that analogs of neurohypophysial hormones administered to gastrointestinal tract preserved their specific physiological activity - they increased solute-free water reabsorption and urinary sodium and potassium excretion. Doses of deamino-vasotocin exerted antidiuretic and natriuretic effects following its oral administration were 50 and 200 times higher compared to maximal effective ones after intramuscular injection. Inhibition of gastrointestinal proteases by aprotinine enhanced effects of nonapeptides; the amount of peptide absorbed from the intestine under these conditions was approximately 0.
View Article and Find Full Text PDFWe have found the physiological mechanism of intensification of the excessive fluid removal from the body under the action of glucagon-like peptide-1 and its analog exenatide. Under the water load in rats, exenatide significantly increased the clearance of lithium, reduced fluid reabsorption in the proximal tubule of the nephron and intensified reabsorption of sodium ions in the distal parts, which contributed to the formation of sodium-free water and faster recovery of osmotic homeostasis. Blocking this pathway with a selective antagonist of glucagon-like peptide-1 receptors slowed down the elimination of excessive water from the body.
View Article and Find Full Text PDFCoevolution - the interaction of different species of animals that are closely related biologically but do not exchange genetic information. The article discusses the problem of coevolution of physiological systems within an organism as the interrelated development of structure, function and systems of their re- gulation during the formation of living systems. We consider the coevolution of osmoregulation and type of metabolism of nitrogen compounds, systemic and individual strategy of coevolution of cell volume re- gulation in poikiloosmotic and homoioosmotic animals, coevolution of effectory organs and endocrine factors in the development of water-salt homeostasis, interrelationship of nonapeptides of neurohypophysis and glucagon-like peptide 1 in regulation of renal function for stabilization of physicochemical para- meters of fluids of the internal environment.
View Article and Find Full Text PDFThe role of subtypes of vasopressin receptors in modulation of renal sodium reabsorption was studied in in vivo experiments on Wistar rats. Selective V1a receptor agonist reduced sodium reabsorption in the kidneys and expression of these receptors increased by practically 100 times. This effect was similar to the effect of furosemide.
View Article and Find Full Text PDFZh Evol Biokhim Fiziol
April 2016
Application of oleamide (final concentration of 10 μM) at the skin basal surface of the frog, Rana temporaria L., augmented the short-circuit current (SCC) from 59.8 ± 2.
View Article and Find Full Text PDFZh Evol Biokhim Fiziol
March 2016
The aim of the present study was to compare effects of glucagon-like peptide-1 (GLP-1) mimetic exenatide on glucose and water-salt homeostasis in animals with different level of renal tubular proximal reabsorption - rats (Rattus norvegicus) and frogs (Rana temporaria). Following glucose tolerance test, in rats exenatide promoted rapid recovery of normoglycemia, whereas in frogs delayed this process. In water-loaded rats exenatide essentially augmented solute-free water clearance and enhanced natriuresis in furosemide-treated rats.
View Article and Find Full Text PDFInjection of a glucagon-like peptide-1 mimetic accelerated recovery of the initial status of water-salt balance in rats after water or saline load (2.5% NaCl). This effect is mediated by a decrease in proximal fluid reabsorption and change in ion and water transport in the distal part of renal tubules.
View Article and Find Full Text PDFRoss Fiziol Zh Im I M Sechenova
July 2015
The aim of the study was a search of physiological approach to restoring osmotic homeostasis in rats with hypernatremia. Intraperitoneal administration of 1.8 ml/100 g BW 2.
View Article and Find Full Text PDFEffects of neurohypophysial nonapeptides of vertebrates (vasopressin, vasotocin, and their synthetized analogues) on urinary magnesium excretion were studied in rats. Neurohypophysial hormones and their analogues at doses stimulating V2-receptors (0.0001-0.
View Article and Find Full Text PDFThe salt-induced peptide formation is important for assessing and approaching schemes of molecular evolution. Here, we present experimental data and an exactly solvable kinetic model describing the linear polymerization of L-glutamic amino acid in water solutions with different concentrations of KCl and NaCl. The length distributions of peptides are well fitted by the model.
View Article and Find Full Text PDFExperiments on Wistar rats showed that exenatide (0.015-0.5 nmol per 100 g body weight) somewhat increased renal excretion of potassium from 7±1 to 16±1 μmol/h/100 g body weight (p<0.
View Article and Find Full Text PDFBull Exp Biol Med
April 2011
Experiments on Wistar rats showed that single intraperitoneal injection nonselective NO-synthase inhibitor L-NAME in a dose of 50 mg/kg was followed by transient proteinuria and albuminuria. This effect was not reproduced by injection of ODQ, an inhibitor of intracellular effects of NO, and arginine, but D-NAME, an optical isomer of L-NAME not blocking NO-synthase, produced similar, though less pronounced effect. The degree of proteinuria and albuminuria increased in combined treatment with nitroarginine methyl esters and 1-deamino-arginine vasotocin or arginine vasopressin.
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