Influence of neurohypophysectomy on the renal actions of aldosterone in the adrenalectomized rat

Abstract

Abstract. The influence of aldosterone administration on urine flow, Na+ and K+ excretion was examined in hypotonic saline infused, Inactin® anesthetised rats following removal of the adrenals or adrenals and posterior pituitary. Plasma adrenal steroid levels were considerably depressed but still detectable 10-14 days after adrenalectomy. Removal of the posterior pituitary markedly reduced Na+ excretion in adrenalectomized animals implying that Na+ retention following neurohypophysectomy is not dependent on adrenal gland function. In adrenalectomized rats aldosterone administration at 42 pmol/min reduced Na+ excretion and urine flow without significantly changing K+ excretion, though plasma K+ was reduced. In adrenalectomized/neurohypophysectomized rats aldosterone further reduced the already low rate of Na+ excretion and increased K+ excretion, though there was no observable effect on urine flow. The results obtained indicate that the Na+-retaining actions of aldosterone are largely independent of posterior pituitary influence. The K+-losing action of aldosterone was, however, only observed in animals in which the posterior pituitary was absent.