Central effects of antiserum against human atrial natriuretic polypeptide on water and electrolyte metabolism and plasma arginine-8-vasopressin level in conscious rats.

Although synthetic atrial natriuretic polypeptide (ANP) is known to influence the water and electrolyte metabolism and arginine-8-vasopressin (AVP) secretion, the physiological role of endogenous ANP in the rat brain is still unclear. Accordingly, an investigation was made of the effects of intracerebroventricular (icv) administration of human h-ANP antiserum, which can neutralize endogenous ANP, on the water intake, urine output, urinary excretion of potassium and sodium, and plasma AVP level in normally hydrated rats. Apart from the water intake, all the parameters were also determined in 48-h water-deprived rats after h-ANP antiserum treatment. The icv administration of the h-ANP antiserum significantly increased the spontaneous water intake, urine output and urinary potassium excretion in rats given water ad libitum. These effects developed by 24 h after icv treatment. The h-ANP antiserum had no effect on the urine volume in 48-h water-deprived rats, suggesting a primary effect of endogenous ANP in the brain on the spontaneous water intake in rats given water ad libitum. These results suggest that ANP may have a physiologically important role in the central regulation of the water and electrolyte metabolism. The h-ANP antiserum did not alter the basal and dehydration-induced AVP release. This raises the possibility that the endogenous ANP in the brain may not participate in the control of AVP secretion.