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

From the ¹ From the Departments of Medicine and Biochemistry, and the Division of Biometry, Western Reserve University, Cleveland, Ohio 44106

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.

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