ACTIVITIES OF LIVER MICROSOMAL FATTY-ACID DESATURASES IN ZINC-DEFICIENT RATS FORCE-FED DIETS WITH A COCONUT OIL SAFFLOWER OIL MIXTURE OF LINSEED OIL

The present study was conducted to investigate the effect of zinc defi ciency on fatty acid desaturation in rats fed two different types of d ietary fat, a mixture of coconut oil and safflower oil (7:1, w/w, ''co conut oil diet'') or linseed oil (''linseed oil diet''). in order to e nsure an adequate food intake, all rats were force-fed by gastric tube . Zinc deficiency caused statistical significant reduction of Delta 9- desaturase activity in liver microsomes of rats fed coconut oil diet a nd tendencial reduction (p < 0.15) in rats fed linseed oil diet compar ed with control rats fed diets with the same type of fat. Ln agreement with this effect, zinc deficiency in the rats fed both types of dieta ry fat increased the ratio between total saturated and total monounsat urated fatty in liver phospholipids and liver microsomes. Zinc deficie nt rats on the coconut oil diet had unchanged Delta 6-desaturase activ ity with linoleic acid as substrate and lowered activity with alpha-li nolenic acid as substrate. Zn contrast, zinc deficient rats on the lin seed oil diet had increased Delta 6-desaturase activity with linoleic acid as substrate and unchanged activity with alpha-linolenic acid. Be cause linoleic acid is the main substrate for Delta 6-desaturase in th e rats fed coconut oil diet, and alpha-linolenic acid is the main subs trate in the rats fed linseed oil diet, it is concluded that in vivo D elta 6-desaturation was not changed by zinc deficiency in the rats fed both types of dietary fat. Activity of Delta 5-desaturase was also no t changed by zinc deficiency in the rats fed both dietary fats. Levels of fatty acids in liver phospholipids and microsomes derived by Delta 4-, Delta 5-, and Delta 6-desaturation were not consistently changed by zinc deficiency in the rats fed both types of dietary fat. Thus, th e enzyme studies and also fatty acid composition data of liver phospho lipids and microsomes indicate that zinc deficiency does not considera bly disturb desaturation of Linoleic and alpha-linolenic acid. Therefo re, it is suggested that similarities between deficiencies of zinc and essential fatty acids described in Literature are not due to disturbe d desaturation of Linoleic acid in zinc deficiency The present study a lso indicates that zinc deficiency enhances incorporation of eicosapen taenoic acid into phosphatidylcholine of rats fed diets with large amo unts of n-3 polyunsaturated fatty acids.