Mammary gland enzyme systems in the study of fatty-acid synthesis.

Abstract

1. Introduction: The role of acetate in fatty-acid synthesis In 1945 Folley and his colleagues (see Foiley 1949, 1952; Malpress 1946) suggested that, in the ruminant, short-chain fatty acids might be synthesized by the lactating mammary gland from acetate. These short-chain fatty acids might then serve as precursors for the synthesis of long-chain acids. Folley & French (1949, 1950) showed that in vitro slices of lactating ruminant mammary gland were able to synthesize fat from acetate, as indicated by a respiratory quotient greater than unity. Non-ruminant lactating mammary tissue was unable to do so, but could utilize glucose for fat synthesis. It was later shown, with the aid of tracers (Balmain, Folley & Glascock 1954) that non-ruminant lactating mammary gland slices could use acetate for the synthesis of fat, provided that glucose was also added. Experiments in vivo laid emphasis upon the synthesis of short-chain fatty acids by the mammary gland. Popják & Beeckmans (1950) showed that injection of [ carboxy - 14 C]acetate into the pregnant rabbit gave rise to a high degree of labelling in the mammary gland fat. Fractionation of these fatty acids (Popják, Folley & French 1950) showed that the label was predominantly concentrated in the short-chain fatty acids, and that this labelling was far higher than that found in the liver fatty acids, indicating synthesis in the gland itself.