Distribution of pyrimidine synthetic enzymes in the rat testis.

The distribution of the de novo and the salvage pathway enzymes for pyrimidine synthesis in the rat testis was investigated in separated seminiferous tubules and interstitial tissue. Aspartate carbamyltransferase (de novo synthesis) was localized primarily in the seminiferous tubules while the uridine and thymidine kinase activities were associated mainly with the interstitial tissue. To further delineate this distribution these enzymes were studied in testes from rats treated with Busulfan (the methane sulfonic acid diester of 1,4-butanediol), which causes degeneration of spermatogonia but not Sertoli cells. The results indicate that a part of the low tubular thymidine kinase activity resides in the germinal elements while the tubular uridine kinase activity is localized in the Sertoli cells.