Role of the Neurohypophysis in Ferritin-Induced Antidiuresis

Abstract

Ferritin-induced antidiuresis in animals (dogs, rabbits) was further studied in dogs to establish mechanisms through which it is mediated. The extent of the antidiuretic response was related to the level of vasoactive ferritin attained in the plasma. A marked discrepancy was observed between amts. of ferritin required by intraven. infusion to produce max. antidiuresis (150-250 [mu]g. ferritin N/kg.) and the residual effective concns. achieved in the plasma (0.0005-0.001 [mu]g./0.5 cc). This disparity is attributed to the effectiveness with which normal liver removes and inactivates circulating ferritin. Evidence was obtained indicating that the antidiuretic action of ferritin is mediated via the neurohypophysis: (a) Antidiuresis was induced by much smaller amts. of ferritin injd. into the carotid artery than are required by the intraven. route. (b) Urine excreted during ferritin-induced oliguria contained antidiuretic material of pitressin-like character to judge from its inactivation by thioglycollic acid. (C) Resection of neurohypophyseal stalk, with development of diabetes insipidus, abolished the antidiuretic action of ferritin in previously responsive dogs.