Biomonitoring of the adverse effects induced by the chronic exposure to lead and cadmium on kidney function: Usefulness of alpha-glutathione S-transferase

A successful prevention of renal diseases induced by occupational exposure to lead (Pb) and/or cadmium (Cd) largely relies on the capability to detect nephrotoxic effects at a stage when they are still reversible or at least not yet compromising renal function. Hence, the aim of this cross-sectional study was to evaluate the usefulness of a set of early biological markers of oxidative stress or nephrotoxicity for the biomonitoring of workers occupationally exposed to Pb and/or Cd in a non-ferrous metal smelter, and gender, age, socioeconomic status, smoking habits, and drug use-matched control individuals. In exposed subjects, mean levels of Pb in blood and urine were also 387.1 ± 99.1 μg Pb/L (1.868 ± 0.478 μmol Pb/L) and 217.7 ± 117.7 μg Pb/g creatinine (1.051 ± 0.568 μmol Pb/g creatinine), and mean levels of Cd in blood and urine were 3.26 ± 2.11 μg Cd/L (0.029 ± 0.019 μmol Cd/L) and 2.51 ± 1.89 μg Cd/g creatinine (0.022 ± 0.017 μmol Cd/g creatinine), suggesting thereby relatively low occupational exposure levels. Statistically significant variations in zinc protoporphyrin, malondialdehyde, retinol binding protein, alpha-glutathione S-transferase, and urinary protein levels were reported between the two groups, and were closely correlated with Pb and/or Cd exposure levels. Variations in αGST levels were closely associated with Pb exposure. Taken together, these results suggest the use of alpha-glutathione S-transferase excretion in urine as a hallmark of early changes in the proximal tubular integrity.