Effects of retinol on glycoprotein synthesis by Sertoli cells in culture: dolichyl phosphomannose synthase activation

Sertoli cells were isolated from Wistar rats aged 19 days and cultured for 48 h. The addition of retinol (10 μM) to the culture medium significantly stimulated the incorporation of [2–³H]mannose into lipid-linked oligosaccharide and into cellular and secreted glycoproteins. Incorporation of [U- 14C] leucine into proteins and of [5, 6–³ H] uridine into RNA was unaffected by retinol treatment. Incubation of microsomal fractions of retinol-treated cells showed an increase in mannose incorporation into dolichyl phosphomannose, into dolichyl pyrophosphoryl oligosaccharide and into proteins. Chromatographic analysis of the fraction soluble in chloroform/methanol (2: 1 v/v) did not show the presence of retinyl phosphomannose either in control or in retinol-treated cells. When the formation of dolichyl phosphomannose was studied in microsomes isolated from control cells and from cells treated with 10 μM retinol for 48 h in the presence of exogenous dolichyl phosphate, the results showed that the retinol effect was due to stimulation of dolichyl phosphomannose synthase.