The effect of dietary fat on fatty acid synthesis in cell-free preparations of lactating mammary gland.

Cell-free preparations of lactating mammary gland of rats maintained during lactation on a fat-free diet incorporated C(14)-acetate into fatty acids to a greater degree than preparations made from rats fed a similar diet containing 20% fat. The type of fat used did not affect the degree of inhibition of synthesis. C(14)-acetate was incorporated mainly into dodecanoic and tetradecanoic acids although labeling was observed in fatty acids from 8-18 carbons. The pattern of labeling was not significantly different in the various groups except for slightly decreased amounts of C(14) in the shorter chain fatty acids of preparations made from glands of rats on the fat-free or coconut oilcontaining diet. The fatty acids characteristic of the fed fat became prominent components of the microsomes and mitochondria as well as of the fat floating on the centrifuged homogenates (presumably milk fat).