Effect of glucose on the major testosterone-maintained protein in the cultured rat ventral prostate

The effect of glucose on the androgen-maintained protein synthesis was studied in the cultured rat ventral prostate. The explants were cultivated for 5 days in the glucose-free medium containing 10% fetal calf serum with or without 10 mM glucose and 10(-7) M testosterone. In some experiments tunicamycin, a specific inhibitor of protein glycosylation was added to the glucose-containing medium. The morphological integrity of the tissue was maintained in all the mediums used. At the end of the culture, the explants were incubated with [35S]methionine. Soluble radioactive proteins were separated by the SDS-polyacrylamide gel electrophoresis and analyzed further by the fluorography. Glucose was necessary for the testosterone-maintained accumulation of three components (Mr less than 14,000) of the major prostatic secretory protein. The electrophoretic migration, glycosylation pattern and immunological data (not shown) indicated that it was the well-known prostatic binding protein. On the other hand, two prominent polypeptides (Mr 70,000 and 100,000) appeared in the absence of glucose. Glucose starvation and the inhibition of glycosylation with tunicamycin caused similar effects on the labelling of the newly-synthesized soluble proteins. The mechanisms of glucose maintenance of the major prostatic protein and suppression of two high molecular weight proteins seemed to be different, although glycosylation was probably involved in both glucose effects.