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.