INFLUENCE OF SODIUM AND POTASSIUM DIETS ON ADRENAL VASOPRESSIN CONTENT AND DIRECT EFFECTS OF VASOPRESSIN ON ALDOSTERONE SYNTHESIS IN ADRENOCORTICAL-CELLS

Two questions were investigated to elucidate the adrenal function of arginine vasopressin (AVP) in controlling aldosterone secretion: Are vasopressin tissue concentrations in the adrenal modulated by diets that influence aldosterone secretion? Does its direct stimulation of aldosterone secretion from adrenal cells in vitro suggest that vasopressin plays an important role in controlling aldosterone? Diets that modulate aldosterone secretion from rat adrenals did not modulate concentrations of AVP in this tissue: Adrenal AVP concentrations did not differ significantly between rats on low- and high-sodium (22.9 +/- 3.8 and 32.4 +/- 6.4 pg/g) or between low- and high-potassium (25.6 +/- 2.5 and 12.5 +/- 7.3 pg/g) diets. Although the existence of AVP receptors on adrenocortical cells incubated in vitro and the stability of AVP during cell incubation was confirmed, AVP had only a minor direct effect on steroid secretion in short-term incubations alone and in combination with angiotensin II (A II), potassium and atrial natriuretic factor (ANF). The importance of AVP for an indirect control of aldosterone secretion in vivo is discussed.