Molecular Pharmacology, Vol 1, 306-311, Copyright © 1965 by the American Society for Pharmacology and Experimental Therapeutics

Oxidation of ¹⁴C-1 and ¹⁴C-6-Glucose by Hormone Synthesizing and Hormone Secreting Portions of Neurohypophysial Neurons

¹ Department of Pharmacology and Therapeutics, University of Manitoba Faculty of Medicine, Winnipeg 3, Canada

The conversion of ¹⁴C-1 of glucose to ¹⁴CO₂ in vitro by bovine posterior pituitary slices was 13-20 times as great as that of ¹⁴C-6; this finding indicates an active hexose monophosphate (HMP) shunt as reported for other endocrine tissues. Nerve endings isolated by centrifugation from the posterior pituitary gave a similar ratio. Tissue obtained from the paraventricular nuclei (PVN) of bovine hypothalamus gave a C-1:C-6 oxidation ratio of 1.1, similar to ratios found in other areas of the brain including the hypothalamus and indicative of glucose oxidation primarily through the Embden-Meyerhof and Krebs cycles. Anterior pituitary slices gave C-1:C-6 oxidation ratios similar to those from posterior lobe, but total glucose oxidation was only 5% to 10% as great. Total glucose oxidation by posterior pituitary tissue was significantly higher than that of brain tissue. Epinephrine, 10^-4 M, stimulated C-1, but not C-6, oxidation in PVN and in anterior and posterior pituitary. The percentage increase in C-1 conversion to CO₂ produced by epinephrine was similar for posterior pituitary slices and for isolated nerve endings. Assuming that the neurohypophysis is representative of endocrine organs in general, it appears that the HMP pathway is concerned with hormone storage and/or secretion rather than with hormone synthesis.

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ACKNOWLEDGMENTS We are indebted to Mr. Elliott Bindler for the preparation of subcellular fractions used in this investigation. This study was supported by USPHS Grant AM-05896, Medical Research Council of Canada, and the American Heart Association.