Changed excretion of urinary proteins and enzymes by chronic exposure to lead

Fifteen various serum and urine parameters were evaluated as indicators of renal alterations induced by lead in 82 male workers of a battery plant chronically exposed to lead (median of blood lead concentration: 2.03 mumol/l). The control group comprised 44 non-exposed healthy volunteers (0.34 mumol/l). High-molecular-mass proteins (transferrin, immunoglobulin G (IgG), (albumin)) were determined in urine as markers of glomerular integrity; low-molecular-weight proteins and parenchymal enzymes (alpha 1-microglobulin, beta 2-microglobulin, retinol-binding protein, lysozyme, ribonuclease, N-acetyl-beta-D-glucosaminidase (NAG), alanine aminopeptidase (AAP), alkaline phosphatase (AP), gamma-glutamyltransferase (GGT)) as indicators of changes in the proximal tubule; Tamm-Horsfall glycoprotein and kallikrein as markers of the distal tubule. There was a positive correlation between tubular indicators and blood lead concentration as well as the erythrocyte protoporphyrin (EPP). About 30% of the lead-exposed workers showed an increased excretion of alpha 1-microglobulin, NAG, ribonuclease, and/or Tamm-Horsfall protein, whereas the glomerular indicators remained unchanged. The combined determination of NAG and alpha 1-microglobulin in urine could be helpful in the early detection of lead-induced changes in the nephron.