Hypoxanthine-guanine phosphoribosyltransferase activity in individual erythrocytes: autoradiographic studies in heterozygotes.

Heterozygotes for the Lesch-Nyhan syndrome have normal hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity in their erythrocyte lysates. However, HGPRT activity in lysates from heterozygotes for the partial HGPRT deficiency states is often between that seen in the affected hemizygote and the normal. An autoradiographic technique was developed which demonstrated the HGPRT activity in individual erythrocytes in vitro. This technique revealed that heterozygotes for the Lesch-Nyhan syndrome had erythrocytes that contained normal HGPRT activity but heterozygotes for the partial deficiency had two populations of erythrocytes, one with normal HGPRT activity and the other with the reduced HGPRT activity characteristic of the hemizygote. With these latter heterozygotes, the proportion of HGPRT-deficient erythrocytes agreed with that calculated on the basis of enzyme activity in erythrocyte lysates.