Assessment of urinary protein 1 and transferrin as early markers of cadmium nephrotoxicity

Abstract

Transferrin and protein 1, a sex linked α2-microprotein, were assayed in urine from 58 workers exposed to cadmium (Cd) in a non-ferrous smelter and from 58 age matched referrents. These two new markers of nephrotoxicity were compared with urinary β2-microglobulin (β2-m), retinol binding protein (RBP), albumin, and β-N-acetylglucosaminidase (NAG). The response of protein 1 to Cd tubulotoxicity was similar to that of β2-m, RBP, and NAG. In Cd workers, protein 1 had a correlation with urinary Cd (r = 0.56) similar to β2-m (r = 0.48), RBP (r = 0.58), and NAG (r = 0.49). Values of these three low molecular weight proteins and of NAG were increased only in workers with urinary Cd higher than 10 μg/g creatinine. Urinary transferrin and albumin were similarly affected by exposure to Cd. Their response, however, was clearly more sensitive than that of low molecular weight proteins. Prevalences of positive values of these two high molecular weight proteins were not only higher but also tended to rise at lower concentrations of Cdr in urine or blood. This finding suggests that in some subjects subtle defects in glomerular barrier function may precede the onset of proximal tubular impairment after chronic exposure to Cd. It remains to be assessed whether these subjects are more at risk of developing renal insufficiency.