Increased urinary adrenomedullin excretion in children with urinary-tract infection

Background. Adrenomedullin(AM), a smooth-muscle relaxant peptide, is stimulated by cytokines and bacterial endotoxins. We hypothesized that urinary-tract infections may be associated with elevated urinary AM excretion. Methods. AM in urine was quantified in eleven children with urinary-tract infection and 11 age- and sex-matched controls by radioimmunoassay. RT-PCR was used to demonstrate local AM mRNA expression in the urinary tract. Results. In healthy controls but not in diseased children there was a significant correlation between AM and creatinine in urine (r = 0.91, P < 0.001). AM levels in children with urinary-tract infection were significantly higher than in controls (0.6+/-0.41 vs 0.15+/-0.14 ng/mu mol creatinine; P<0.001; (means+/-SD)). There was a significant correlation between white cell count and AM in urine (r = 0.75, P<0.001). AM mRNA was expressed in renal tissue, renal pelvis, ureter, bladder, and urethra. Conclusion. The smooth-muscle relaxant peptide adrenomedullin that is synthesized in tissue of the human urinary tract is elevated in urine of patients with urinary-tract infections. A possible consequence might be the interference with the ureteral anti-reflux mechanisms.