Resumo

ARZOLA, J et al. La Oxitocina media la natriuresis inducida por la Angiotensina II administrada centralmente. AVFT [online]. 2005, vol.24, n.2, pp.22-30. ISSN 0798-0264.

The renin angiotensin system (RAS) is considered to play an important physiological role in the regulation of body fluid. Intracerebroventricular administration of renin or angiotensin II (Ang II) increases blood pressure, sympathetic outflow, water intake, sodium excretion and oxytocin and vasopressin release and decreases urine volume. Evidence indicates tha oxytocin is a natriuretic hormone. Thus, with the use of a specific oxytocin receptor antagonist, atosiban (AT), we evaluated the role of oxytocin as a possible effector in the natriuretic action induced by intracerebroventricular (ICV) administration of Ang II or renin. Our results demonstrate that Ang II-ICV administration reduced urinary volume at 1 hour of collection and increased urinary excretion of sodium, potassium and cGMP at 1-, 3- and 6 hrs period of urine collection. Atosiban potentiated the Ang II antidiuretic effect and blunted natriuresis, kaliuresis and increased cGMP excretion induced by ICV-Ang II. The increase in urinary cGMP was independent of the stimulation of nitric oxide synthase activity, since L-NAME pretreatment did not modify the renal actions induced by ICV-renin. Our results support the concept that oxytocin mediated the natriuretic action of the brain renin angiotensin system.

Palavras-chave : Angiotensin II; Atosiban; Natriuresis; Oxitocin; Nitric oxide.