Transient assay, by [3H]guanine incorporation of Escherichia coli xanthine-guanine phosphoribosyl transferase (GPT) in transfected human fibroblasts.

We have used [3H]guanine incorporation as a rapid and sensitive assay of xanthine-guanine phosphoribosyl transferase (GPT) activity in SV40 transformed human fibroblasts. The SV40 early promoter is more efficient than the Rous sarcoma virus long terminal repeat for transient expression of the gpt gene. The assay works well in a derivative of AT5BIVA which lacks hypoxanthine-guanine phosphoribosyl transferase (hprt-) and we show here how the assay has been adapted to work in the hprt+ AT5BIVA parent.