The effect of methyl sterculate on oleic acid synthesis in the hen

The enzymic desaturation of saturated fatty acids to monoenes in animals and plants is inhibited by cyclopropene fatty acids, such as sterculic acid. Labeled acetic and stearic acids were administered to laying hens which had received methyl sterculate in the diet for long periods, and the incorporation of the label in the eggs and liver was studied. The egg was used as a “biological trap” to study the metabolism of the hen in relation to its diet. Maximum incorporation of label was observed in the third or fourth egg laid after administration of the labeled compound. Dietary methyl sterculate reduced the incorporation of stearic acid into egg yolk lipids, but the incorporation of acetate was not affected. The formation of oleic acid was inhibited by methyl sterculate irrespective of whether the prescursor was acetate or stearate acid. In laying hens receiving methyl sterculate for long periods, no evidence could be obtained for the biosynthesis of oleic acid by an alternative pathway which did not involve the desaturation of stearic acid. The validity of comparing the ratio of the specific activities of stearic acid and oleic acid in control birds with the corresponding ratio obtained for birds receiving methyl sterculate is questioned, because the sizes of the metabolic pools of the product and precursors may be quite different for the two groups of birds.