INCREASED SECRETION OF BRAIN NATRIURETIC PEPTIDE AND ATRIAL-NATRIURETIC-PEPTIDE, BUT NOT SUFFICIENT TO INDUCE NATRIURESIS IN RATS WITH NEPHROTIC SYNDROME

The levels of immunoreactive brain natriuretic peptide (ir-BNP) and immunoreactive atrial natriuretic peptide (ir-ANP) were evaluated by radioimmunoassay in both the atrium, ventricle and plasma of adriamycin-induced nephrotic rats and control rats. There was no difference in right and left atrial concentrations of ir-BNP, however, a higher right atrial concentration of ir-ANP was observed in nephrotic rats than in controls (p < 0.01). The ventricular ir-BNP and ir-ANP were increased in nephrotic rats compared to controls (BNP: p < 0.001, ANP: p < 0.001). Cardiac BNPs were composed of pro-BNP (γ-BNP) and its C-terminal 45-amino-acid peptide (BNP-45). The ratio of BNP-45 γ-BNP in nephrotic rats was higher than that of controls in both atria and in the ventricle. Plasma ir-BNP and ir-ANP were significantly higher in nephrotic rats than in controls (BNP: p < 0.001, ANP: p < 0.001), and each level was negatively correlated with urinary sodium excretion in nephrotic rats (BNP: r = -0.84, p < 0.001, ANP: r = -0.88, p < 0.001). These results suggest that production and secretion of both BNP and ANP are concomitantly stimulated by a decreased renal ability to eliminate sodium and water, but this secretion is insufficient to induce effective natriuresis in nephrotic rats. © 1991.