Serum Calmodulin Activity in Male Lead-exposed Workers

Abstract

Serum calmodulin (CaM) activity was studied in 75 lead exposed and 21 non-exposed male workers. The lead-exposed workers were divided into groups with low blood lead (BPb < 50 μg/dL) and high blood lead (BPb ≥ 50 μg/dL). The concentrations of lead, calcium, magnesium, copper, zinc, and free erythrocytic protoporphyrin (FEP) in blood were determined. Serum samples were heated in a water bath (100° C) for 3 minutes arid centrifuged for 15 minutes at 4° C (18,000 × g). The supernatants obtained were used to measure CaM activity. The results showed that: 1) Average blood lead concentrations in workers with both low and high levels of exposure were significantly higher than those in controls (p < 0.05). 2) Serum CaM activity in the high-exposure group (31.09 ± 7.84 μg/dL) was significantly lower than that in controls (78.11 ± 15.13 μg/dL,p < 0.05). The biological threshold of BPb inhibition of CaM activity was less than 50 μg/dL. 3) Multiple correlation analysis showed a negative dose-response relationship between BPb and CaM activity. The step wise regression procedure indicated that lead had negative, and calcium and magnesium positive, effects on serum CaM activity. The regression equation was Y = 66.1383 – 1.0857 X_l + 2.9676 X₂ + 5.2222 X₃ (Y:CaM; X_l:Pb; X₂: Ca; X₃:Mg). These results of the first such study carried out in male lead-exposed workers suggest that lead can inhibit CaM activity in humans.

Keywords:

• male workers
• lead exposure
• blood lead
• serum calmodulin