Contribution of the Pentose Cycle to Glucose Metabolism by Adrenal Cortexin Vitro

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Abstract
Slices of beef adrenal cortex incubated in vitro with glucose -1-C14 and 6-C14 yield a C14O2 ratio of carbons 1 to 6 of 5.9, and this decreases to 3.3 in the presence of ACTH. ACTH increases the oxidation of carbons 1 and 6 of glucose to CO2 and decreases their incorporation into glycogen. The ratio of incorporation of carbons 1 to 6 into glycogen is one. Corticosteroid concentration in the medium increases 2- to 3-fold on ACTH addition. Under these conditions, there is a 10% contribution of the pentose cycle to over-all glucose metabolism. This estimate is derived from the extent of randomization of carbon 2 of glucose during its incorporation into glycogen and depends upon a model for calculation in which a complete pentose cycle is assumed to exist. Evidence in support of this model is obtained from the occurrence of the same ratio of C14O2 yields from fructose-1-C14 and 6-C14 as from glucose-1-C14 and 6-C14.