Erythrocyte arginase activity as an indicator of lead exposure

Abstract

A semi-automated method has been developed for the determination of the arginase activity of erythrocytes using dried blood spots, which are easy to prepare on site in a factory for later laboratory analysis. The mean arginase activity of erythrocytes in 49 men occupationally exposed to lead was 62.9 IU/g.Hb (SD, 14.4 IU/g.Hb); in 45 men not exposed to lead the mean was 44.6 IU/g.Hb (SD, 11.6 IU/g.Hb). A significantly higher mean arginase activity was found in the specimens from lead-exposed workers (p < 0.001). The correlation coefficient between blood lead and erythrocyte arginase was r = 0.67 (p < 0.001). The degree of correlation between blood lead and lead indicators including arginase was r = 0.75 for urine δ-aminolaevulinic acid, r = 0.67 for erythrocyte arginase, r = 0.66 for urine lead, and r = 0.63 for coproporphyrin. Erythrocyte arginase showed no significant correlation in the liver function tests, GOT, GPT, and albumin in serum. When 40 μg/100 g of blood lead concentration was fixed as the basic value and 56.2 IU/g.Hb of erythrocyte arginase activity was set as the screening value in lead-exposed workers, the sensitivity and specificity of the arginase test were 0.96 and 0.65, respectively. Thus the validity of the test was calculated to be 1.61. These results show that the arginase level of erythrocytes can be considered to be one of the significant indicators of occupational exposure to lead because it reflects well the dose-response relationship of lead in the human body. Our method allows rapid analysis of erythrocyte arginase and thus should be useful in screening for lead exposure.