| Abstract: | An ultra-microchemical method using radioactive substrates has been developed for enzyme activity measurements at the single cell level. In order to demonstrate the possibilities of this radiochemical microassay, activity measurements of hypoxanthine-guanine phosphoribosyl transferase (HG-PRT) and of adenine phosphoribosyl transferase (A-PRT) in isolated human fibroblasts are described. There was a linear relationship between the number of cells incubated and the enzyme activities found. It was observed that the HG-PRT activity in single, skin derived, fibroblasts did not differ from that in amniotic fluid derived fibroblasts, thus providing a new, quantitative assay for rapid prenatal diagnosis in the Lesch-Nyhan syndrome. |
