Biosynthesis of fatty acids by slices and cell-free suspensions of mammary gland

Abstract

The biosynthesis of fatty acids from acetate in tissue slices and cell-free suspensions of rat and sheep mammary gland were studied. In tissue slices, in addition to glucose, pyruvate and members of the citric acid cycle stimulated fatty-acid synthesis from acetate. These substances were particularly effective with slices of sheep udder. Cell-free suspensions of mammary gland of lactating rats and sheep can synthesize fatty acids from (carboxy-C14) acetate. In suspensions of rat mammary gland 3 conditions are required for fatty-acid synthesis: aerobic incubation; oxidation of either pyruvate, oxaloacetate or alpha-oxoglutarate; and addition of adenosine triphosphate (ATP) to some extent. The best results were obtained in the presence of oxaloacetate and ATP and when the gas-phase was air instead of pure O2. All the saturated n-fatty acids containing an even number of C atoms from 6 to 18 and also oleic acid were synthesized in the rat mammary suspensions. Suspensions of sheep udder used acetate for fatty-acid synthesis even without further addition, although oxaloacetate had a stimulating effect in this prepn. also, but ATP in a concn. of 0.01 M inhibits fatty-acid synthesis. While the suspension of sheep udder oxidized appreciable amts. of acetate, suspensions of rat mammary gland were virtually inactive in this respect. Implications of the results are discussed.