Androgenic Regulation of Metabolic Pathways in the Rat Epididymis

Abstract

The metabolic activity of slices of epididymal tissue was studied in vitro and a comparison made between androgen-maintained rats (with ligated efferent ducts) and androgen-deprived rats (following castration). Two regions of the epididymis were examined, namely the caput and cauda. The androgen-deprived epididymis consumed O2 at about half the rate of the androgen-maintained organ. The pentose phosphate cycle was also considerably less active in the epididymis of castrated rats, being 36% and 14% of that in the caput and cauda, respectively, of efferent-duct-ligated rats. In contrast, the rates of aerobic glycolysis did not differ greatly between the 2 animal treatments although the rate was somewhat higher in the caput of androgen-deprived rats. While the rate of glucose consumption was increased by excluding O2 from androgen-deprived tissue, little change was observed with androgen-maintained tissue. The possibility that this result was caused by differential penetration of glucose into the tissue slices was excluded by conducting similar incubations with isolated epididymal cells. With tissue slices, lactic acid production was increased in all incubations by the exclusion of O2 and accounted for all the glucose consumed. Determinations of respiratory quotient indicated that under aerobic conditions the epididymis from androgen-deprived animals used carbohydrate almost exclusively as an energy source. In contrast, the epididymis from androgen-maintained animals derived a considerable proportion of its energy from the oxidation of lipids, about 2/3 in the caput and 1/3 in the cauda epididymidis. The androgen-maintained epididymis derives its energy largely by the oxidation of lipids, but is unable to increase its glycolytic rate under anaerobic conditions, while the androgen-deprived epididymis depends more on glycolysis and adapts to anaerobic conditions by increasing its glycolytic rate.