Zum Einfluß von Zinkdepletion auf die Gehalte einzelner Phospholipide in der Erythrozytenmembran und deren Fettsäurezusammensetzung bei zwangsernährten Ratten

Supplementation with vitamin C, vitamin E or beta-carotene influences osmotic fragility and oxidative damage of erythrocytes of zinc-deficient rats

Dietary zinc deficiency in rats causes increased osmotic fragility of their erythrocytes. In this study, the influence of supplementary antioxidants (vitamin C, vitamin E or beta-carotene) on osmotic fragility, oxidative damage and components of the primary defense system of erythrocytes of zinc-deficient rats was investigated. Indicators of hemolysis in vivo were also examined. Five groups of 12 male rats were force-fed a zinc-adequate diet (control rats), a zinc-deficient diet or a zinc-deficient diet enriched with vitamin C, vitamin E or beta-carotene. Compared with the control rats, the rats fed the zinc-deficient diet without supplementary antioxidants had greater red blood cell osmotic fragility, higher concentrations of thiobarbituric acid-reactive substances and alanine, higher glutathione S-transferase activity, lower concentration of glutathione and activity of glutathione peroxidase as well as lower activity of superoxide dismutase in plasma (P < 0.05). Supplementation with antioxidants generally improved osmotic fragility in zinc-deficient rats without influencing zinc concentration or alkaline phosphatase activity in plasma, indicators of zinc status. At some of the hypotonic saline concentrations tested, vitamin C and beta-carotene significantly affected osmotic fragility. The zinc-deficient rats fed a diet without supplementary antioxidants had significantly higher concentrations of alanine in erythrocytes than the zinc-deficient rats supplemented with vitamin C, vitamin E or beta-carotene and had significantly higher levels of thiobarbituric acid-reactive substances in erythrocytes than the rats supplemented with beta-carotene. There was no indication of hemolysis in vivo in rats fed zinc-deficient diets. The results show that supplementary antioxidants decrease osmotic fragility and oxidative damage of erythrocytes in zinc-deficient rats.

[The effect of zinc deficiency on heart and brain lipids in rats force-fed with coconut oil or fish oil diets]

The present study investigated the effect of zinc deficiency on lipid concentrations and fatty acid composition of heart and brain in force-fed rats receiving either a diet with coconut oil and safflower oil (86:14, w/w) or a diet with fish oil and safflower oil (91:9, w/w). Four groups of growing male Sprague-Dawley rats were fed 11.6 g of a semisynthetic diet containing either 0.8 mg Zn/kg or 111 mg Zn/kg with either coconut oil and safflower oil or fish oil and safflower oil per day by gastric tube for 10 days. Concentrations of lipids in heart as well as fatty acid composition of heart phospholipids and brain total lipids were determined. Zinc deficient rats fed the coconut oil diet had higher concentrations of triglycerides (16.3 mg/g vs. 9.21 mg/g) and total fatty acids (29.3 mg/g vs. 21.8 mg/g) in heart than control rats fed coconut oil diet, whereas concentrations of phospholipids and total cholesterol were not different between zinc deficient and control rats. Concentrations of lauric acid (12:0), myristic acid (14:0), palmitic acid (16:0), palmitoleic acid (16:1), and oleic acid (18:1) were by 65 to 192% higher in hearts of zinc deficient rats fed coconut oil diet than in control rats fed coconut oil diet. In contrast, concentrations of triglycerides, phospholipids, total cholesterol, and total fatty acids in heart were similar in zinc deficient rats and control rats fed fish oil diet. The fatty acid composition of heart phospholipids was only slightly influenced by zinc deficiency in the rats fed both types of dietary fat. The level of arachidonic acid in phospholipids which may represent desaturation activity was not different in the zinc deficient rats and control rats fed coconut oil diet, and was only slightly reduced in zinc deficient rats fed fish oil diet compared to control rats fed fish oil diet. This finding suggests that zinc deficiency does not impair delta-5 and delta-6 desaturation of linoleic acid in heart. Concentrations of fatty acids in brain as well as fatty acid composition of brain total lipids was only slightly influenced by zinc deficiency. This suggests that short-term zinc deficiency does not affect fatty acid metabolism of brain.

[The effect of zinc depletion on the fat content and fatty acid composition of the liver and brain in forcibly fed rats]

In the present work the influence of zinc deficiency on fat content and fatty acid composition of liver and fatty acid composition of brain of rats with a high food intake was investigated. Using the force-feeding technique the rats were fed 14.5 g food daily at days 1 to 4, and then 11.6 g food for later days. After 7 days the zinc-deficient animals had a fatty liver which was characterized by an increase in fat content (68%) and dry matter (23%). The amounts of lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, and oleic acid were also increased by 100 to 200% in the liver of zinc-deficient animals, whereas the amount of arachidonic acid was decreased by 29%. The amounts of phosphatidylcholine and phosphatidylethanolamine in the liver were not changed by zinc deficiency, but the fatty acid composition of these phospholipids was changed. The liver phospholipids of zinc-deficient animals had a decreased proportion of arachidonic acid, but an increased proportion of docosahexaenoic acid. In the zinc-deficient animals there also existed a positive correlation between the fat content in the liver and the ratio between linoleic and arachidonic acid in the liver and a negative correlation between the fat content in the liver and the amount of arachidonic acid in the liver. These correlations as well as the changes in liver fatty acid composition of zinc-deficient animals suggest that the fatty liver might be the result of a disturbed metabolism of linoleic acid. In contrast, zinc deficiency did not influence the fatty acid composition of brain. This means that brain is protected against the effects of short-term zinc deficiency.