Atrial Natriuretic Peptide Suppresses Osmotically Stimulated Plasma Arginine Vasotocin Levels in the Pekin Duck

Abstract

Plasma arginine vasotocin (AVT) concentrations were measured at 15-min intervals in conscious Pekin ducks intravenously infused with 1 M saline at a rate of 0.5 ml/min for 1 hr. The responses were compared in eight birds, each given in random order a polyclonal antiserum against atrial natriuretic peptide (anti-ANP) or normal rabbit serum (control). The elevations in plasma osmolalities and sodium concentrations and the reductions in hematocrit values caused by the hypertonic saline were similar in both conditions. Plasma ANP in the control animals was elevated threefold during the saline infusion (from 66.8 ± 8.8 pg/ml to a peak of 193.3 pg/ml), whereas in the same birds treated with specific antiserum, circulating ANP concentrations fell to less than 10 pg/ml and remained at this level for the duration of the experiment. Plasma AVT concentrations rose steadily and significantly from basal levels of 5.8 ± 0.5 and 5.8 ± 0.8 pg/ml in the control and anti-ANP groups, respectively; however, the concentrations measured in the birds with low plasma ANP were consistently higher ( P < 0.02) than those under the control condition. Furthermore, the sensitivity of AVT release for the control birds (0.35 pg/ml per mOsm/kg) was significantly lower ( P < 0.001) than that in the anti-ANP animals (0.86 pg/ml per mOsm/kg). Elevated plasma ANP may suppress osmotically stimulated AVT release during states of vascular volume expansion.