THE EFFECT OF HYPOPHYSECTOMY, REMOVAL OF THE POSTERIOR PITUITARY, ADRENALECTOMY, AND DEHYDRATION ON THE ANTIDIURETIC ACTIVITY OF THE RAT HYPOTHALAMIC-NEUROHYPOPHYSEAL SYSTEM

Abstract

Antidiuretic activity was measured in the hypothalamic-neurohypohyseal system of male rats (approximately 200 g) after subjecting the animals to various experimental conditions, such as dehydration, both by saline injection and by water deprivation, adrenalectomy, complete hypophysectomy, and removal of the posterior lobe of the pituitary. Of the various conditions employed, those involving dehydration were the only ones to cause a marked change in the concentration of the antidiuretic substance in the neurohypophysis. The fact that the concentration of the antidiuretic substance in the supraoptic area remained unchanged under these same conditions would seem to indicate that the antidiuretic substance was being formed in the supra-optic area and then stored in and released from the posterior pituitary. Evidence was obtained that the presence of the posterior lobe of the pituitary as an activator is not necessary necessary for the hypothalamic material to display antidiuretic activity. A decrease in the quantity, of the antidiuretic substance was noted in the hypothalamus and in the remaining portion of the neurohypophysis 34 days after hypophysectomy and 19 days after removal of the posterior lobe. The evidence that the antidiuretic substance in the hypothalamus and neurohypophysis is not altered several days after adrenalectomy and yet has been reported to increase in the circulatory system, supports the suggestion that there may be decreased destruction of the substance by the liver rather than increased production of the hypothalamic-hypophyseal system.