To clarify the role of vitamin E in the modulation of macrophages, we investigated its effect on O_2^- and PGE_2 production in macrophages. Macrophases isolated from vitamin E-treated rats, and containing an extremely high level of α-tocophrol, showed lower O_2^- and PGE_2 production following stimulation with PMA or calcium ionophore A23187 compared to those of control macrophages. We also investigated the mechanism by which vitamin E inhibits both O_2^- and PGE_2 production in macrophages, by measuring the activities of protein kinase C and phospholipase A_2 in intact macrophages and cell-free homogenate system. Vitamin E did not directly inhibit phospholipase A_2 activity but inhibited phospholipase A_2 activation through phosphorylation and translocation of the enzyme itself in the intracellular signal transduction. From these results, it was concluded that the action of vitamin E was due to indirect inhibition of NADPH oxidase and phospholipase A_2 activities through the signal transduction system such as protein kinase C and intracellular Ca^<2+>.

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Although the methods of high-performance liquid chromatography with electrochemical detection for the determination of vitamin K (K_s) in human plasma had already reported, they have some problems including the effect of dissolved oxygen in mobile phase on background current, losing sensitivity of electrode due to adsorption of reducted compounds on to the surface of the electrode, and single determination for phylloquinone (K_1). For the resolution of these problems, we tried to use a platinum black column for the reduction of K_s instead of electrochemical reduction, and an amperometric electrochemical detector in the oxidation mode. Therefore, we developed a sensitive method for the simultaneous determination of K_1 and menaquinons (MK-4, MK-7) in human plasma. The detection limits in the present method were 0.05 ng/ml of K_1, MK-4 and 0.1 ng/ml of MK-7.

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All-trans-retinyl β-glucuronide (ROG) which is water soluble was chemically synthesized and studied its biological activity. Weanling wistar male rats were fed on a vitamin A deficient diet for 30 days, and divided into 3 groups. Each rat in the 1st group was orally given with 5.2 μmol of ROG on the last day, animals in the 2nd group were given with vitamin A acetate (A-ace), and the 3rd group was remained as a vitamin A deficient control. At 48 hours after administration, retinol contents in liver and serum of rats were determined. Serum retinol levels in rats given with ROG significantly increased, but not in liver. However, serum retinol levels of ROG group were lower than those of A-ace group. Then, the effect of ROG on growth of the young rats was examined as compared with A-ace, and vitamin A deficiency. Rats in each group were orally given with 21 nmol/day of ROG or A-ace for 28 days. ROG supported the growth of young rat, although its ability was inferior to A-ace. And ROG was also effective to recover the body weight loss of rats with vitamin A deficiency. These results show that animals could convert ROG into retinol in vivo, and ROG has activities as the vitamin A.

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