ROLE OF ENDOGENOUS ATRIAL-NATRIURETIC-PEPTIDE IN VOLUME EXPANSION DIURESIS AND NATRIURESIS OF THE PEKIN DUCK

Polyclonal antibodies raised in a rabbit against avian atrial natriure tic peptide (ANP) were shown to reduce circulating endogenous ANP leve ls in Pekin ducks by more than 90%, and were subsequently used to inve stigate the role of this peptide in volume expansion diuresis and natr iuresis. Conscious birds, undergoing a steady-state diuresis and natri uresis maintained by an i.v. infusion of hypotonic saline at a rate of 0.7 ml/min, responded to ANP antiserum (anti-ANP) with an immediate 3 0% reduction in urine flow rate and sodium excretion which lasted for about 30 min. Plasma arginine vasotocin levels were not changed by ant i-ANP whereas circulating angiotensin II concentrations increased imme diately following the administration of anti-ANP. Serum from non-immun ized normal rabbits produced no changes in the renal and plasma parame ters monitored. The results show that the high circulating levels of e ndogenous ANP associated with volume expansion promote renal salt and fluid excretion and thus have a major physiological role in avian volu me homeostasis.