Evaluation of Urinary N- acetyl-β-D-glucosaminidase (NAG) and Glutathione-S-transferase (GST) Activities as Early Markers of Occupational Lead Nephropathy in an African Population

• I.O Omotosho

Although application of urinary enzymes as markers of diseases in excessive metal exposure is not novel, it is not popular in this part of
the world. Urinary NAG and GST activities were evaluated to detect covert kidney damage in Lead (Pb) exposed (LES), chronic renal
failure (CRF) and in clinically normal subjects (Control) in a prospective study using standard methods. Concentration of traditional
markers of renal function (plasma creatinine, urea and uric acid) for the above group of subjects were found to be grossly normal despite
about 18% of the LES showing excessive ingestion of Pb. Mean urinary NAG activities of 10.2±1.7U/l, 12.4±3.8U/l and 14.8±6.3U/l
were obtained for the control, LES and CRF subjects respectively. Also, 4.4% of LES and 15.3% of CRF subjects had urinary NAG
activity higher than that of the control (17±5.8); the difference was not significant (P≥0.05). Mean urinary GST activity of 39±25.9μg/l,
76±27.7μg/l and 102±54.5μg/l were obtained for the control, LES and CRF subjects respectively. In particular, 91% of LES group and
83% of CRF subjects exhibited higher urinary GST activity relative to the control (39±25.9μg/l); the difference was significant (p≤0.05).
These data suggest that Urinary GST has the potential of being a better indicator of early kidney damage in Pb exposed subjects than
urinary NAG; its result correlated better with that of blood lead level used as the main marker of occupational Pb exposure in this study.

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