Glucose stimulation of testosterone-maintained protein synthesis in the rat ventral prostate

Abstract

The stimulatory effect of exogenous glucose on protein synthesis maintained by testosterone was studied by measuring the in vitro incorporation of amino acids into proteins in the rat ventral prostate. The addition of glucose did not influence the specific activity of the extracellular or intracellular amino acid pools. The amount of newly-synthetized proteins was increased in the presence of glucose. Mannose was as effective as glucose, whereas a variety of other substrates (e.g. pyruvate, lactate, amino acids, acetate) which are readily metabolized by the prostate, failed to support to the same extent hormoneactivated protein synthesis. None of the substrates increased protein synthesis in the prostate of castrated rats. The incubation of the prostate without any substrate led to a decline in the level of ATP, the ATP/ADP ratio and the adenylate energy charge and to a rise in the levels of ADP and AMP irrespective of the hormonal state of the tissue. The addition of glucose restored the levels and ratios of the adenine nucleotides, but several other substrates were also able to maintain the initial ATP levels in the prostate of castrated, as well as castrated, testosterone-treated rats. The stimulatory effect of glucose on hormone-maintained protein synthesis cannot be explained by changes in the adenine nucleotides. Nevertheless, the activation of glucose metabolism may play an important role by providing energy for increased synthetic reactions. Moreover, glucose and mannose molecules themselves or a glycolytic metabolite (proximal to pyruvate) may be required for the full expression of the transcriptional effect of testosterone on protein synthesis in the ventral prostate of castrated rats.