Red-cell pyrimidine 5'-nucleotidase and lead poisoning.

In an effort to determine its value as a biological index of lead poisoning, we investigated the red-cell pyrimidine 5'-nucleotidase (Py5N) activity, along with the classical parameters, in 22 subjects with varying degrees of lead intoxication. In all cases, the red-cell Py5N activity was found to be decreased, even when most of the other biological tests of lead intoxication remained negative. Below the level of 150 microgram of lead per 100 ml of blood, the magnitude of the red-cell Py5N decrease was roughly proportional to the level of lead in peripheral blood. We conclude that red-cell Py5N is a convenient, reliable and sensitive index of lead exposure.