CREATINE METABOLISM IN THE SEMINIFEROUS EPITHELIUM OF RATS - I - CREATINE SYNTHESIS BY ISOLATED AND CULTURED-CELLS

The testis synthesizes creatine from both arginine and glycine precurs ors, but when rat testicular tissue is separated into seminiferous tub ules and interstitial cells, creatine synthesis occurs only in the tub ular fraction. The purpose of the work presented here was to define th e locus of creatine synthesis within the seminiferous tubules, by usin g cell separation and culture techniques to examine synthesis in the S ertoli cells and germ cells. The total creatine content, in the cellul ar compartment and incubation medium, of Sertoli-germ cell co-cultures and of Sertoli cell-enriched cultures, largely free of germ cells, in creased by similar amounts over a 24 h incubation period. Sertoli cell -enriched cultures incorporated radioactivity from L-[guanidino-C-14]a rginine and [1-C-14]glycine into both creatine and its biosynthetic pr ecursor, guanidinoacetic acid. Isolated germ cells did not incorporate radioactivity from L-[guanidino-C-14]arginine into either creatine or guanidinoacetic acid when incubated at a similar density and protein concentration under similar conditions. It is concluded that the synth esis of creatine osberved in isolated rat seminiferous tubules occurs within the Sertoli cells and not the germ cells.