[Physiologic importance of atrial natriuretic peptide in volume expansion and hypertension: experimental studies]

The release of atrial natriuretic peptides (ANP) is stimulated by acute volume expansion. In order to elucidate the importance of the ANP release for the physiological response to volume expansion, a monoclonal antibody was used in rats. This antibody against ANP specifically blocks the ANP effects in vivo. The acute natriuresis induced by isotonic volume expansion is blocked by the antibody. However, the excretion of an additional sodium load (saline with an additional amount of 50 mmol/l sodium) is not entirely ANP-dependent. Acute volume expansion induces a dramatic decrease of plasma renin activity and a slight decrease of plasma aldosterone concentration measured 5 min after volume expansion. These effects are blocked by simultaneous administration of the monoclonal antibody. The endogenous level of ANP that can be reached in volume expansion is thus sufficient for suppression of the renin-aldosterone system. The physiological importance of ANP underlined in these volume expansion experiments raises the question of its role in pathophysiological states such as hypertension. In old, spontaneously hypertensive rats (SHR) ANP plasma levels and relative heart weights are higher than in age-matched normotensive Wistar Kyoto rats (WKY).(ABSTRACT TRUNCATED AT 250 WORDS)