Plasma arginase concentration measured by an enzyme-linked immunosorbent assay (ELISA) in normal adult population

Human liver arginase has many biological effects on lymphocytes, macrophages, liver cells, and tumor cells, in addition to its major role in the liver urea cycle. We have developed a sandwich enzyme-linked immunosorbent assay (ELISA) method to quantitate arginase concentrations in plasma that can be applied to various body fluids. The sensitivity was 2.5 ng/mL. The coefficients of variation were good both in intra- and inter-assay. Using this method to study the stability of an arginase preparation, we found that plasma arginase was stable for only 1 or 2 days even at temperatures as low as 4 degrees C. The mean plasma level was 41.0 +/- 3.3 ng/mL (mean +/- SE) in 143 normal subjects. There was no age difference in the general population and in the male group. However, in the female group, the plasma arginase level increased with age (p = 0.05). Its biological significance was unclear. As a whole, the ELISA method for the measurement of arginase concentration in the body fluid is convenient and reliable.