Abrupt changes of water and sodium excretion in normal and adrenalectomized dogs

¹ Department of Physiology, Harvard Medical School, Boston, Massachusetts

An experiment was designed to induce rapid changes in sodium and water excretion. With this procedure normal dogs showed a prompt and marked water diuresis, with an accompanying antinatriuresis. The same dogs, adrenalectomized and maintained on constant adrenal cortical hormone therapy, demonstrated an identical response despite the constancy of steroid concentration, suggesting a ‘permissive’ action of the hormones. When the animals were deprived of therapy for several days the excretion patterns of sodium and water did become markedly abnormal. Acute replacement with hydrocortisone restored the water excretion pattern to normal but did not correct the abnormal sodium excretion pattern. Aldosterone, given prior to and during the experiment, failed to restore either the water or sodium excretion patterns. The results obtained with acute replacement of hydrocortisone and aldosterone were identical with those obtained with hydrocortisone alone.