Propionate metabolism by slices of mammary gland and liver of lactating rat.

Lipogenesis from propionate-l-Cl4 was first reported by Feller and Feist (2) in slices of liver and adipose tissue. Favarger and Gerlach (3, 4) and Masoro and Porter (5) recently studied the incorporation of propionate-1-V into fatty acids of rat and mouse adipose tissue in viva and in vitro. The incorporation of propionate, compared with that of acetate, was quite low. Favarger and Gerlach (4), on degrading the fatty acids formed from propionate, found labeling to be mainly in pentadecanoic and heptadecanoic acids, with propionate providing the terminal methyl 3-carbon unit. James, Peeters, and Lauryssens (6) found, after perfusion of cow udder with propionate-1-C14, a small amount of labeled oddand even-numbered carbon fatty acids in butterfat. Synthesis of odd-numbered carbon acids from propionate by a cell-free fat-synthesizing enzyme preparation has been reported (7). We have studied propionate metabolism by slices prepared from the mammary glands and livers of lactating and nonlactating rats. In this paper, studies on lipogenesis from, and the oxidation of, V-labeled propionate and succinate by preparations from lactating rats are described.