EFFECTS OF ATRIAL-NATRIURETIC-FACTOR ON NOREPINEPHRINE RELEASE EVOKEDBY ANGIOTENSIN-II AND ANGIOTENSIN-III IN THE RAT ADRENAL-MEDULLA

Atrial natriuretic factor (ANF) effects on neuronal norepinephrine (NE ) release evoked by angiotensin II(ANG Il) or angiotensin III (ANG Ill ) were studied in the rat adrenal medulla. ANF 10 nM diminished the in crease of NE release induced by ANG II (1 mu M), ANG III (1 mu M) or 1 00 mM KC1. When 10 mM ANF was added to the medium containing KC1 plus ANG II or KC1 plus ANG III, the reduction of 3H-NE output by ANF was g reater than when the atrial factor was added to the medium containing only ANG II or ANG III. Since both ANG II and ANG III have a physiolog ical role on catecholamine metabolism, these peptides could modulate t he adrenal medulla functions. ANG II and ANG III enhance NE release an d decrease NE uptake in the rat adrenal medulla. Present results show that ANF is a physiological antagonist of both ANG II and ANG III, in the process of NE secretion. The interaction between ANF and the renin -angiotensin system could contribute to the regulation of the adrenal medulla catecholamines pathway and sympathetic activity.