INTERACTION OF ZINC AND ESSENTIAL FATTY-ACIDS IN THE RAT

Three experiments were performed to investigate the possibility of a physiological relationship between zinc and essential fatty acids (EFA). Male weanling rats were fed diets low in zinc, EFA or both and their growth rates, dermal scores and tissue fatty acid profiles determined. In experiment 1, a basal soybean protein diet containing 7 ppm of added zinc and approximately 300 ppm EFA was used in a 2 x 2 factorial design: low Zn-low EFA; adequate Zn-low EFA; low Zn-adequate EFA and adequate Zn-adequate EFA. The low zinc status accentuated signs of EFA deficiency, including dermal lesions and growth rate, but it had no significant effect on the fatty acid profile in plasma. In experiment 2, a basal casein diet containing approximately 25 ppm of EFA and less than 1 ppm of zinc, was used in a similar design. For 7 weeks two groups of weanling rats were fed ad libitum either a diet adequate in Zn and low in EFA or a diet adequate in all nutrients. From 7 to 12 weeks zinc was removed from one-half of each group and all were pair-fed to the intake of the low zinc-low EFA group. Zinc deficiency accentuated dermal lesions in the group deprived of EFA and abd caused enlarged joints suggestive of an arthritic-like syndrome. In experiment 3, an egg albumin based diet containing approximately 25 ppm EFA and less than 1 ppm of zinc was used in a 2 x 2 factorial design. No signs of fatty acid deficiency occurred in 5 weeks with adequate zinc. Zinc and EFA deficiency accentuated dermal scores and severely depressed growth. Zinc deficiency increased the proportion of arachidonic acid in foot skin especially in the EFA deficient group. It is concluded that there is a physiological interaction between Zn and essential fatty acids.