Hexosemonophosphate shunt in endocrine tissues. Quantitative estimation of the pathway in bovine pineal body, anterior pituitary, posterior pituitary, and brain

Abstract

The activity of the hexosemonophosphate shunt was estimated quantitatively in pineal body, anterior pituitary, posterior pituitary, and brain cortex, extending earlier observations which indicated the presence of the hexosemonophosphate pathway in these organs. The contribution of the hexosemonophosphate shunt to total glucose catabolism was determined from the specific yield of CO 2 from [I- 14C]glucose and [6- 14C]glucose. Total glucose utilization was measured by summing 14C found in CO 2, lactate, fatty acids, and glycerol and by measuring the depletion of non-labelled glucose from the medium. In the anterior pituitary, posterior pituitary and pineal body, 5%, 4% and 3% of the utilized glucose, respectively, is catabolized via the hexosemonophosphate shunt, whereas in brain the activity of the pathway is negligible. The rate of glucose utilization is fairly constant over the incubation periods in all four tissues, being highest in brain, and least in anterior pituitary, with posterior pituitary and pineal body giving intermediate values.