Effect of dietary copper deficiency. in the rat on fatty acid composition of adipose tissue and desaturase activity of liver microsomes.

1. Male rats were maintained from wearing to between 4 and 16 weeks of age on a semisynthetic diet which was deficient in copper. 2. Methyl esters of fatty acids from adipose tissue of the rats were analysed by gas-liquid chromatography and the desaturase activity of liver microsomes, with [1-14C]=stearic acid as the substrate, was determined. Liver and plasma Cu concentration, cytohrome c oxidas (EC 1.9.3.I) activity and caeruloplasmin activity were determined as indices of Cu status. 3. Cu deficiency was associated with decreased mono-unsaturated:saturated ratios for C16 and C18 fatty acids from subcutaneous adipose tissue and decreased desaturase activity for liver microsomes. When Cu-deficient rats were given free access to the Cu-adequate diet or were injected intraperitoneally with an aqueous solution of CuSO4, that is, when the animals were related with Cu, the indices of Cu status, and desaturase activity for liver microsomes returned to values found in control animals. 4. When Cu or a Cu-chelator (Neocuproine) was added to microsomes, there was no effect on the activity of the desaturase enzyme system; the stability of the desaturase was not affected by Cu. 5. These results are indicative of an involvement of Cu in the desaturase reaction. It is suggested that the site of this involvement could be the terminal component of the microsomal electron transport chain.