In vitro Evidence for an Inhibitory Effect of Atrial Natriuretic Peptide on Vasopressin Release

The effect of Arg-atriopeptin III (ANP) on basal and stimulated (angiotensin II, acetylcholine and KC1 depolarization) arginine vasopressin (AVP) release was characterized in the intact hypothalamo-neurohypophysial explant (HNS) and in isolated neurointermediate pituitary lobes (). In initial experiments using 15-min incubation periods, ANP 10–10 and 10–9M slightly inhibited basal AVP release in both and HNS after a delay of at least 15 min. The most effective ANP concentration was 10–10M, and the inhibitory effect on AVP release was more marked in HNS (–52 ±5% of control compared to –29 ±8% for ). However, ANP 10–l0M did not significantly attenuate KCl- or AII (10–5M)-stimulated AVP release from HNS after 15 min of exposure. When the incubation periods were increased to 30 min ANP 10–10 and 10–9M significantly decreased All-stimulated (105M) AVP release in a dose-dependent manner (p –5M) AVP release (p