In 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<0.001) was revealed between renal excretion of oxytocin and sodium ions. Under the action of oxytocin, natriuresis was characterized by diminished reabsorption of fluid in the proximal tubule of the nephron attested by elevated lithium clearance rate and from stimulation of V1a receptors in the cells of thick ascending loop of Henle. Pmp-Tyr(Me)-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH2, a V1a receptors antagonist, prevented the natriuretic effect of oxytocin.
Keywords: V1a receptor; kidney; natriuresis; oxytocin; proximal reabsorption.