FRACTIONAL CLEARANCES OF LOW-MOLECULAR-WEIGHT PROTEINS IN LEAD WORKERS

Urinary alpha(1)-microglobulin (alpha(1)-m) and beta(2)-microglobulin (beta(2)-m) can be used as early indicators of renal tubular dysfuncti on. However, low levels of lead exposure cause an increase in urinary alpha(1)-m, but not in urinary beta(2)-m. In order to clarify the leve l of tubular dysfunction in early lead nephropathy, fractional clearan ces of alpha(1)-m (FC-alpha(1)-m) and beta(2)-m (FC-beta(2)-m), i.e., the ratios of these clearances to the creatinine clearance, were measu red in 99 male lead workers. Blood urea nitrogen, serum creatinine, ur ic acid, and urinary creatinine and N-acetyl-beta-D-glucosaminidase ac tivity were also measured to diagnose the presence of other renal dysf unction. The median of FC-alpha(1)-m was 0.13% in the control group. T he FC-alpha(1)-m increased in lead workers with blood lead (B-Pb) leve ls above 20 mu g/dl. The correlation of FC-alpha(1)-m with urinary alp ha(1)-m was highly significant, but there was no correlation with seru m alpha(1)-m. The median of FC-beta(2)-m was 0.065% in the control gro up. There was a correlation of FC-beta(2)-m with FC-alpha(1)-m, but th ere was no correlation with B-Pb, or with serum beta(2)-m. These resul ts suggest the following: There was a very low excretion rate of alpha (1)-m and beta(2)-m in both the control group and the lead exposed gro ups. The excretion rate of alpha(1)-m was higher than that of beta(2)- m. There seemed to be slight a dysfunction of tubular reabsorption in the lead workers, and the elevation of alpha(1)-m excretion reflected the dysfunction more sensitively than the elevation of beta(2)-m excre tion in lead poisoning.