Atrial content and plasma levels of atrial natriuretic peptides in rats with chronic renal failure

The possible role of atrial natriuretic peptides (ANP) for the adaptive changes in renal Na excretion during chronic renal failure was studied in 5/6 nephrectomized (NX) rats maintained on a normal (100 mmol/kg) and a high (800 mmol/kg) Na diet. Atrial content of natriuretic substances was determined by bioassay and plasma ANP by radioimmunoassay. Nephrectomized rats showed a twofold increase in plasma ANP irrespective of their Na intake. Atrial ANP content was increased by high Na diet but unchanged by NX. Nephrectomized rats maintained on high Na diet showed partial depletion of atrial ANP stores. There were no significant changes in the volume fraction of atrial granules determined. The results suggest that ANP is involved in the regulation of renal Na excretion during chronic renal failure and acute Na loading; other mechanisms are probably involved in the adaption to chronic Na loading.