Biosynthesis of fatty acids in cell-free homogenates of lactating gerbil mammary gland.

Abstract

AbstractCell‐free homogenates of lactating mammary gland of gerbils maintained on a diet of sunflower seed, guinea pig chow and oats (Diet 1) or a diet of guinea pig chow and oats (Diet 2) and of rats maintained on laboratory chow (Diet 3) were incubated with14C‐labeled acetate, acetyl CoA or malonyl CoA aerobically. A large proportion of the14C from14C‐acetate and14C‐acetyl CoA incorporated into fatty acids by homogenates from gerbils on Diet 1 was in unsaturated compounds, particularly in 18‐carbon and 20‐carbon dienoic acids, compared to preparations from animals on Diets 2 or 3. The two radioactive dienoic acids were proven to be Δ9,12 18∶2 and Δ11,14 20∶2, and the latter was shown to be a direct elongation product of Δ9,12 18∶2 by the substrate14C‐acetyl CoA. In all experiments14C from14C‐malonyl CoA was incorporated predominantly into 14∶0 and 16∶0, and very little incorporation occurred into unsaturated fatty acids in homogenates made either from gerbil or rat. Total fatty acids isolated from homogenates and from milk fat (fat floating on the centrifuged homogenates) of gerbils on Diet 1 had a higher proportion of 18∶2 than animals on the other two diets, a reflection of the large dietary intake of linoleic acid by gerbils on Diet 1. Under these conditions the amount of 18∶2 in the mammary gland had a significant effect on the products of the incubation.