Increased plasma levels of mature adrenomedullin in chronic glomerulonephritis

Adrenomedullin (AM) is a potent vasodilative and natriuretic peptide that i s processed from its precursor as the intermediate form, AM-glycine-COOH (i AM). Subsequently, iAM is converted to the biologically active mature form, AM(1-52)-CONH2 (mAM), by enzymatic amidation. Using immunoradiometric assa ys that recognize total AM (tAM) and only mAM, we determined the plasma and urinary levels of mAM and iAM in patients with chronic glomerulonephritis (CGN). The plasma mAM concentration was significantly higher in the patient s than in the controls (1.8 +/- 0.1 vs. 1.3 +/- 0.1 fmol/ml, p < 0.01), whe reas the plasma iAM concentration of the CGN patients did not significantly differ from that of the controls (9.4 +/- 0.5 vs. 8.9 +/- 0.5 fmol/ml). Le vels of urinary mAM excretion in the patients did not statistically differ from those of the controls (1.6 +/- 0.4 vs. 2.0 +/- 0.3 fmol/ mg creatinine ), whereas urinary iAM excretion was significantly lower in the CGN patient s (3.7 +/- 0.7 vs. 5.6 +/- 0.8 fmol/mg creatinine, p < 0.05). Urinary excre tion levels of mAM significantly correlated with those of sodium (r = 0.47, p < 0.05), whereas those of iAM did not. In conclusion, the plasma ratio o f mAM to iAM is augmented in CGN patients, and mAM appears to be involved i n the regulation of sodium. Therefore, determination of the mAM in addition to the tAM concentration is essential in CGN patients. Copyright (C) 2000 S. Karger AG, Basel.