Mechanism of action of neurohypophyseal hormones on sodium excretion and diuresis

Administration of pituitrin, vasopressin, and oxytocin to rats during spontaneous micturition increases diuresis and sodium excretion by reducing tubular reabsorption. In adrenalectomized rats these preparations have no diuretic effect and increased sodium excretion is observed only after administration of vasopressin. After hypophysectomy the diuretic effect of the preparations disappears but they still increase sodium excretion. It is postulated that the diuretic effect of the neurohypophyseal hormones is connected with activation of the pituitary-adrenal system, whereas some additional mechanism is involved in their effect on sodium excretion.