Conjoint action of sodium and angiotensin on brain mechanisms controlling water and salt balances.

Abstract

AbstractAndersson, B. and L. Eriksson, Conjoint action of sodium and angiotensin on brain mechanisms controlling water and salt balances. Acta physiol. scand. 1971. 81. 18–29.The effects on water and salt balances of a simultaneous infusion of angiotensin and hypertonic NaCl into the 3rd brain ventricle were studied in goats in normal water balance and in hydrated animals. For comparison similar infusions of angiotensin alone (solved in slightly hypotonic saline) and of hypertonic NaCl were made. Like the hypertonic NaCl, 30 min infusions of angiotensin alone induced drinking in animals in normal water balance, and an inhibition of the water diuresis in the hydrated goat. The simultaneous infusion of both substances resulted in a marked potentiation of the dipsogenic and the antidiuretic effects. A possible explanation may be that angiotensin facilitates the transport of Na+ into brain cells regulating thirst and ADH release, and that the intracellular Na+ concentration rather than strictly osmotic factors determines the activity of these cells. In the hydrated goat a central effect of angiotensin strongly enhanced the natriuretic response to intraventricular infusions of hypertonic NaCl, and extreme natriuresis developed as result of the combined infusions in hydrated, salt‐supplemented animals. During normal water balance this sodium‐angiotensin synergism was less obvious, which suggests that both an expanded fluid volume and an elevated intracellular Na+ concentration are needed for optimal activation of a brain mechanism which stimulates renal Na' excretion, The time course of the centrally induced natriuresis indicates that the effect on the kidney may be mediated by a humoral agent.