Increased vasopressin secretion: an early manifestation of aging in the rat

Vasopressin release and renal water conserving capacity were measured in normal Long-Evans rats ranging in age from 2 to 17 months. Twenty-four hour urine volume rose and urine osmolality fell as the animals aged, with the first differences evident by age 10 months. Assessment of vasopressin release from isolated hypothalamic-neurohypophysial units by means of an in vitro perifusion system demonstrated that hormone discharge increased as the animals aged, being evident by age 7 months. The increased vasopressin releasability could not be attributed to the greater vasopressin content present in the posterior pituitary of the older rats. The data suggest that increased vasopressin secretion is an early manifestation of aging in the rat and that the consequent hypervasopressinemia may affect the renal tubule with resultant diminished responsiveness to the hormone.