A simple quantitative micromethod of arginase assay in blood spots dried on filter paper.

An accurate, precise and sensitive method has been developed for measurement of arginase activity in erythrocytes in dried blood spots. The assay is based on colorimetric measurement of ornithine produced by enzymatic hydrolysis of L-arginine. Only 10 microliter of capillary blood collected on filter paper are required. One disc of 3 mm in diameter punched from the dried blood spot is used for the arginase assay. The whole procedure is performed in one test-tube and does not need deproteinization. The second disc of the same diameter is used for hemoglobin (Hb) measurement. There was a good correlation between activities determined in dried blood spots and fresh erythrocytes of the same blood specimens taken from 101 healthy adults and 49 children (corre. coeff. 0.955 and 0.968, respectively). Arginase activity in dried blood specimens was 68.3 +/- 22.7 in adults and 62.7 +/- 15.7 U/g Hb in children. In 118 newborns, the activity was 101.9 +/- 29.2. In 1270 residents of nursing homes screened for hyperargininemia the activity was 21.5-171.2 U/g Hb. In screening for arginase deficiency, the method may be used as a simplified qualitative test without Hb assay.