Effect of glucose deprivation on the incorporation of 3H precursors into pituitiary glycoproteins and on basal LH, FSH and prolactin release

Abstract

Glucose can serve as a precursor for all of the components of the oligosaccharides of glycoproteins. The incorporation of various 3H precursors into glycoproteins was examined by incubating rat anterior pituitaries in vitro for 4h in the presence and absence of glucose. Substituting succinate for glucose enhanced the incorporation of D-(2- 3H)mannose six-fold, the incorporation of D-(1, 6- 3H)-glucosamine two-fold and the incorporation of D-(6- 3H) galactose was enhanced slightly. The incorporation of other 3H precursors was unalterted or reduced by glucose deprivation. Rat anterior pituitaries incorporated minimal quantities of N-acetyl-D-(6- 3H)mannosamine, the immediate precursor of N-acetyl-D-neuraminic acid, into glycoproteins. Glucose deprivation also stimulated the 4h basal release of LH and FSH by 58% and 95%, respectively, as well as stimulated net intracellular degradation of prolactin. Thus, glucose deprivation enhances the incorporation of some, but not all, 3H precursors into glycoproteins as well as stimulates the basal release of LH and FSH.