EVIDENCE THAT ENDOGENOUS ARGININE-VASOPRESSIN (AVP) IS INVOLVED IN THE MAINTENANCE OF THE GROWTH AND STEROIDOGENIC CAPACITY OF RAT ADRENAL ZONA GLOMERULOSA

A 7-day subcutaneous infusion with the AVP antagonist (Deamino-Pen1, V al4, D-Arg8]-vasopressin (AVP-A; 3 nmol.kg-1.min-1) significantly lowe red plasma aldosterone concentration in rats, without affecting the pl asma levels of ACTH and corticosterone. Prolonged AVP-A treatment caus ed a marked atrophy of adrenal zona glomerulosa (ZG) and its parenchym al cells, without inducing any significant change in zona fasciculata morphology. Isolated ZG cells from AVP-A-infused rats evidenced a nota ble decrease in both their basal and maximally-stimulated aldosterone production. The simultaneous infusion of rats with AVP (3 nmol.kg-1.mi n-1) completely reversed all these effects of AVP-A. These findings su ggest that endogenous AVP may be specifically involved in the maintena nce of the growth and steroidogenic capacity of rat adrenal ZG. Moreov er, they seem to indicate that under basal conditions the pituitary-ad renal-glucocorticoid axis is independent of AVP release.