The role of plasma osmolality, angiotensin II and dopamine in vasopressin release in man.

A sensitive and specific radioimmunoassay for arginine vasopressin was used to compare the relative importance of changes in plasma osmolality, angiotensin II and dopamine in the regulation of vasopressin secretion in man. One hour after water loading plasma vasopressin fell from 0.40 to 0.06 pmol/l, while 8 h and 24 h fluid restriction resulted in a rise of vasopressin from 0.29 to 0.54 and 1.37 pmol/l respectively. In contrast neither dietary sodium deprivation, when plasma angiotensin II increased 5-fold, nor dopamine infusion, at a rate which increased circulating dopamine levels up to 244-fold, had any effect on basal plasma vasopressin values. These results confirm that, under physiological conditions, osmoregulation is the major mechanism controlling vasopressin release and suggests that circulating angiotensin II and dopamine have no significant part to play.