Estimation of the Glucuronic Acid Pathway Contribution to Glucose Metabolism in Adipose Tissue and the Effect of Growth Hormone

A definite contribution of the glucuronic acid pathway to total glucose metabolism by rat adipose tissue in vitro in the presence of growth hormone preparations has not been found. Randomization of 14C of glucose-5-14C into glycerol and glucose-1-14C and -2-14C into glycogen on incubation of rat epididymal tissue indicates that the pathway contributes at most only a few per cent to the over-all metabolism of glucose. Results of incubations with glucose-1-14C and -6-14 are in accord with metabolism solely via the pentose cycle, Embden-Meyerhof pathway, and Krebs cycle. Thus, essentially all of the 14C utilized on incubation of glucose-1-14C and -6-14C is isolated in products formed via these pathways. Nonequilibration of dihydroxyacetone phosphate with glyceraldehyde 3-phosphate occurs, and this results in a preferential oxidation to CO2 of carbon 6 as compared to carbon 1 via the Krebs cycle. This coupled with an increase in the fraction of carbon 3 of pyruvate converted to CO2 and a decreased pentose cycle contribution in the presence compared to the absence of the preparations can account for the enhanced yields of 14CO2 from glucose-6-14C as compared to -1-14C that have been reported on growth hormone addition.