Myron Brin

Mechanisms of lipid peroxidation in erythrocytes of vitamin E-deficient rats and in phospholipid model systems

Abstract Erythrocytes from vitamin E-deficient and control rats were peroxidized by glucose oxidase-glucose or dialuric acid. Losses of polyunsaturated fatty acids from membrane phospholipids, and of dimethylacetals from plasmalogens, were quantitated by gas-liquid chromatography. Similar treatment of solubilized or micellar phospholipids or plasmalogens in vitro showed that in both erythrocytes and micellar systems, arachidonic acid and the 16-carbon plasmalogen are most susceptible to peroxidation by either reagent. The same narrow concentration range of dialuric acid found effective in peroxidizing erythrocytes from tocopherol-deficient rats was also found effective in peroxidizing micellar phospholipids in vitro . Partially peroxidized erythrocytes from tocopherol-deficient rats were subjected to treatment with phospholipase A or phospholipase C. Hemolysis by either phospholipase was accelerated in partially peroxidized cells as compared to controls, suggesting that peroxidation exposes both polar and nonpolar lipid sites in the erythrocyte membrane.

Drug metabolism and hepatic heme proteins in the vitamin E-deficient rat

Abstract Hepatic microsomes prepared from vitamin E deficient and supplemented rats were analyzed for cytochrome P-450 content and drug metabolizing activity. Reduced levels of benzo[α]pyrene hydroxylase and ethylmorphine N -demethylase activities were observed in microsomes derived from rats fed a diet deficient in vitamin E compared to those of control rats. NADPH-mediated destruction of P-450, and pentobarbital and zoxazolamine sleeping times were similar in the two groups. Induction with 3-methylcholanthrene raised the levels of benzo[α]pyrene hydroxylase activity of both supplemented and deficient rats to the same absolute levels. No differences were noted in cytochrome P-450 or P-448 content between control and tocopherol deficient rats, nor did the activity of liver catalase differ between the two dietary groups. Thus, these studies did not demonstrate any impairment of heme protein synthesis in vitamin E deficient rats.

Pyridoxine and oral contraceptives.

Tryptophan loading tests were performed to determine how much pyridoxine hydrochloride must be given to women taking oral contraceptives to correct their heightened excretion of xanthurenic acid. 43 women 33 of whom took the pill participated for 3 months. 2 gm of tryptophan was administered orally on 3 occasions per cycle and an 8 hour urine sample was analyzed for xanthurenic acid. Pyridoxine was administered during cycles 1 and 3 at doses of 2 5 10 or 20 mg. Placebo was given in the second cycle and 5 women in each group took no medication. Xanthurenic acid excretion ranged from 0 to 32 micromoles/8 hours in those not on the pill after tryptophan load but averaged 167.5 micromole/8 hours in pill users after tryptophan. The pyridoxine doses of 10 mg daily corrected some women and 20 mg corrected most womens excess xanthurenic acid excretion. The authors recommended that 30 mg pyridoxine be given to women on the pill. This is far in excess of the daily allowance of 2 mg/day recommended by the United Kingdom Department of Health.

A rapid micromethod for the functional evaluation of vitamin E status in rats with the Fragiligraph

Abstract A preliminary report of this work has appeared (42). A rapid microassay for functional vitamin E status in the rat has been developed using small amounts of whole blood. A peroxide-generating system such as glucose oxidase and glucose or ascorbic acid and sodium azide is coupled with osmotic hemolysis of erythrocytes in the Fragiligraph. Values obtained for displacement of the fragiligram in tocopherol deficiency are correlated with plasma tocopherol values and with hemolysis values obtained with dialuric acid. As rats fed a tocopherol-deficient diet became more depleted in tocopherol, a progressively larger displacement of the fragiligram was observed. This technique is particularly applicable in laboratory situations requiring a rapid assay for vitamin E status because it requires only 50 μl of peripheral blood and can be completed in approximately half an hour.

Drug-Diet Interactions

We live in a chemical world. From the beginning of time this chemical environment was either the source or result of hfe itself. Therefore our environment contained ozone, carbon monoxide, nitrosamines, etc., long before the industrial era.

The Functional Evaluation of Vitamin Status with Special Attention to Enzyme-Coenzyme Techniques

Following the discovery that there were essential dietary nutritional factors such as vitamins which if not consumed in adequate quantities would result in severe clinical deficiency diseases, and that these diseases could be cured by repletion with the essential nutrients, it soon became evident that the public health problem of nutritional adequacy should be managed by techniques of preventive medicine. Accordingly, an estimate of the vitamin status of the population was needed. With that information one could judge the necessity for intervention programs.