Quantification of the activity of neutral endopeptidase (NEP), a marker enzyme of the proximal tubular brush border membrane, in urine of patients in earlier stages of the nephropathy, and in patients with severe renal failure (end-stage) due to AA administration revealed a 45% and 90% reduction of the NEP activity, respectively, compared to healthy control subjects. The gene discussed is MME; the disease is Renal insufficiency.