Surface-associated glycosyltransferase activities in rat Sertoli cells in vitro

We have previously demonstrated fucosyltransferase (FT) activity on mouse germ cell surfaces at different stages of spermatogenesis. To complement these findings, here we report FT activity on the Sertoli cell (SC) surface. SC isolated and cultured from 20-day-old rat testes displayed FT activity with a Vmax of 12.5 pmoles/mg protein/min and a Km of 22 microM, while purified Sertoli cell plasma membranes (SCPM) showed FT activity with a Vmax of 10 pmoles/mg protein/min and a Km of 18.2 microM for GDP-[14C]-L-fucose. Fucosyltransferase activities were 16.7 and 2.6 pmoles/mg protein/min in SC and SCPM, respectively; approximately 16% of FT activity is, therefore, on the cell surface. To test whether the expression of FT activity in SC was regulated by hormones and growth factors, SC were cultured in serum-free medium supplemented with insulin, transferrin, sodium selenite, and epidermal growth factor (medium 4F) or in 4F plus follicle-stimulating hormone, testosterone, hydrocortisone, and vitamin E (medium 8F). We found that FT activity in SC is not modulated by these hormones or growth factors (4F or 8F). For comparison with FT, galactosyltransferase (GalTase) activities in SC and SCPM were also determined. SC displayed GalTase activity with a Vmax of 50 pmoles/mg protein/min and a Km of 38.5 microM, while SCPM showed GalTase activity with a Vmax of 25 pmoles/mg protein/min and a Km of 20.8 microM for UDP-[3H]-galactose. Galactosyl-transferase activities were 29.2 and 9.6 pmoles/mg protein/min in SC and SCPM, respectively. Therefore, approximately 33% of the total cell GalTase activity was detected on the surface membranes of rat Sertoli cells.(ABSTRACT TRUNCATED AT 250 WORDS)