In Vitro Conversion of Long-Chain Fatty Acids to Ketones by Bovine Rumen Mucosa

The rate of conversion of laurie, myristic, palmitie, stearic, oleic, and linoleie acids to ketone bodies by rumen mucosal tissue from five normal and five fasted nonpregnant, nonlaetating Holstein heifers was studied in vitro. Endogenous formation of ketone bodies occurred in tissue from both groups of animals. The net rate of ketone formation in the presence of exogenous longchain fatty acids was significantly faster (P < 0.01) in tissue from fasted animals than from control animals, but the extent of conversion of the exogenous substrates to ketones was of small magnitude in tissue from both groups. The fatty acids containing 12, 14, and 16 carbon atoms tended to be more ketogenie than the 18 carbon acids. Results of two additional in vitro incubation experiments, in which ~"C-labeled palnfitie and oleie acids were used as substrates, conclusively showed that ketones were derived directly from the long-chain fatty acids.