Adrenal cortex and neurohypophyseal deficiency in salt and water homeostasis of rats

¹ Department of Anatomy, The University of British Columbia, Vancouver, Canada

The role of adrenal cortex and neurohypophysis in controlling the equilibrium distribution and handling of water, sodium, and potassium was studied for a 2-week period in rats deprived of these glands. Adrenal deficiency is characterized by a loss of sodium from both extracellular and intracellular compartments (gastrocnemius, aorta) and a shift of water into cells. The sodium gradient, [Na]o/[Na]i, remains relatively unchanged. There is a marked fall in the potassium gradient, [K]i/[K]o, due in large part to the shift of water and in smaller part to a translocation of potassium. Neurohypophyseal deficiency is characterized mainly by an increase in intracellular sodium both in amount and concentration. A salt load administered by stomach tube tends to be excessively retained when cell sodium is low and excessively rejected when it is high. Animals deprived of both adrenal and neurohypophyseal function show an intermediate pattern. The pattern of salt and water distribution in either deficiency thus depends in part on the activity of the remaining gland. It is suggested that adrenal insufficiency and diabetes insipidus are counterpoint states.