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Journal of Lipid Research, Vol. 14, 678-687, November 1973
Copyright © 1973 by Lipid Research, Inc.

Fatty acid oxidation and esterification in isolated rat hepatocytes: regulation by dibutyryl adenosine 3',5'-cyclic monophosphate

Charles J. Homcy and Simeon Margolis

Clayton Laboratories, Department of Medicine, and Department of Physiological Chemistry, The Johns Hopkins University, Baltimore, Maryland 21205

Isolated rat hepatocytes rapidly utilized [¹⁴C]palmitate and, in particular, synthesized large amounts of neutral lipids from palmitate. Incorporation into cellular lipids occurred at a linear rate proportional to the medium concentration of fatty acids. Oxidation of [¹⁴C]palmitate to CO₂ increased with time and was much slower than palmitate esterification. Since [¹⁴C]acetate and [¹⁴C]glucose were oxidized to CO₂ at a linear rate, the lag in fatty acid oxidation to CO₂ did not involve enzymatic steps subsequent to acetate formation. The relative contribution of palmitate to esterification and to CO₂ formation depended upon the molar ratio of palmitate to albumin (v) and the length of incubation. Dibutyryl cyclic AMP (1 mM) reduced the oxidation of palmitate and acetate to CO₂ by about 50 and 90%, respectively, but did not alter palmitate esterification. However, equivalent concentrations of sodium butyrate produced similar decreases in CO₂ formation. Dibutyryl cyclic AMP (1 mM) also stimulated palmitate oxidation to water-soluble products, principally ketone bodies, by 50-100%. Sodium butyrate exerted no effect, while monobutyryl cyclic AMP and cyclic AMP both stimulated this pathway significantly. These results indicate that both v and dibutyryl cyclic AMP regulate the metabolism of fatty acids by isolated hepatocytes and suggest that hormonal stimulation of adenyl cyclase controls hepatic lipid metabolism.

Supplementary key words acetate oxidation • fatty acid concentrations • butyrate • glucose oxidation

Submitted on August 30, 1972
Revised on June 28, 1973
Accepted on July 30, 1973

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