RELATIONSHIP BETWEEN PENAL MASS AND ATRIAL-NATRIURETIC-PEPTIDE RELEASE .2. ACUTE EFFECTS OF VARIOUS DEGREES OF RENAL DAMAGE ON ATRIAL-NATRIURETIC-PEPTIDE RELEASE IN RATS

We studied basal serum atrial natriuretic peptide (ANP) levels and the response to acute salt loading in rats with different grades of funct ional renal mass reduction. The six groups of rats studied included 2 controls, i.e. unoperated (n=12) and sham-operated (n=24) groups. Each of the 4 experimental groups (n=24 in each) underwent one of the foll owing procedures: bilateral nephrectomy; unilateral nephrectomy; bilat eral ureteral ligation; unilateral ureteral ligation. Basal ANP was as sessed in the intact controls and operated groups 4, S, 16 and 24 h af ter surgery. In addition, ANP was determined in the sham-operated cont rols and in the experimental groups 1 h following acute intravenous sa line loading performed 4 h after surgery with central ve nous pressure monitoring. B as al ANP dropped significantly following bilateral nep hrectomy but was not significantly altered after unilateral nephrectom y or the two modalities of ureteral ligation. In all 4 experimental gr oups ANP failed to rise after saline loading. We conclude that substan tial renal damage results in early impairment in ANP secretion suggest ing the existence of a renal physiological stimulus controlling ANP re lease by cardiac atria.