The Cascade System of Osmotic Homeostasis Regulation

The 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. After water loading and the injection of 0.015 nM exenatide (GLP-1 mimetic), the time of excretion of 50% of water was halved from 112 ± 4 to 57 ± 5 min ( p < 0.01), and after the injection of 0.015 nM oxytocin, it decreased to 83 ± 6 min ( p < 0.01). The physiological mechanism of renal effect of the aforementioned hormones which accelerate the recovery of osmotic homeostasis has been found.