This communication has described the relationship between steroid cataract and vitamin E (E) in an in vitro steroid cataract model based on the following results that we have obtained so far. When isolated rat lenses were incubated in TC-199 culture medium containing methylprednisolone (MP) (1.5 mg/ml) over a 72-h period, a faint opacity appeared in the equator at 12 h after culture initiation and whole cortical opacity occurred at 72 h. E level decreased at 72 h after culture initiation, while a decrease in reduced glutathione (GSH) level and an increase in lipid peroxide (LPO) level occurred at 48 h or later. The activity of glyceraldehyde-3-phosphate dehydrogenase ( GAP-DH ), an index of oxidative damage, decreased at 24 h after culture initiation or later. Na^+/K^+ ratio increased before opacity formation. This increase was enhanced as opacity progressed. An increase in water content and a decrease in Na^+, K^+-ATPase activity were seen at 48 h after culture initiation or later. Simultaneous treatment with E prevented MP-induced lens opacification. When lenses cultured with MP were treated with E at 24 and 48 h during the culture period of 72 h, the treatment at 24 h, but not at 48 h, was effective. E level in lenses treated with MP and E, irrespective of the timing of E treatment, increased with an increase in culture time and this increased E level was much higher than that in either lenses treated with MP alone or untreated lenses. When lenses with the same severity of MP-induced early cortical opacity were further cultured in medium containing MP and E for 48 h, opacity progression was prevented. The opaque lenses further cultured with MP alone showed a decrease in E level and an increase in water content in addition to further increases in LPO level and Na^+/K^+ ratio and further decreases in GSH level and GAP-DH and Na^+, K^+ -ATPase activities. The changes in these components and enzymes except GSH were attenuated in the opaque lenses further cultured with MP and E. These results indicate that MP-induced cataract is closely related to E in cultured rat lenses and that E can prevent the progression of this MP-induced cataract through its antioxidative and membrane-stabilizing actions. Thus, it canbe anticipated that E becomes an anti-cataract drug for steroid cataracts.

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The nutritional efficiencies of the intermediates of the tryptophan-niacin pathway and the related compounds of nicotinic acid and nicotinamide as a substitute for nicotinic acid were investigated using weanling rats fed the niacin-deficient diet. Judging from the growth response, levels of liver NAD, blood NAD, and urinary excretion of nicotinamide and its metabolites, we have concluded that tryptophan, 3-hydroxyanthranilic acid, quinolinic acid, nicotinamide N-oxide, N'-methylnicotinamide, nicotinuric acid, 3-acetylpyridine, pyridine 3-aidehyde, pyridine 3-methanol, β-picoline, or nicotinic acid N-oxide is approximately 1/10, 1/12, 1/24, 1/5, 1/2, 1/10, 1/10, 1/1, 1/1, 1/10, or 1/2 active as nicotinic acid, however, that N-formylkynurenine, kynurenine, 3-hydroxykynurenine, anthranilic acid, cinchomeronic acid, 3-cyanopyridine, 6-hydroxynicotinic acid, and pyridine 3-sulfonic acid do not have any niacin activity. Only 6-aminonicotinamide of the examined compounds showed the very strong antagonistic activity against niacin.

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We have examined the plasma and urinary levels of vitamin C after oral administration of calcium ascorbate preparation in six healthy males(20〜27 years). They were given a preparation A or B in a two-period crossover trial. A contains 363 mg of calcium ascorbate and 700 mg of ascorbic acid, and B contains 1000 mg of ascorbic acid. The mean plasma concentration of vitamin C at 1 and 2 h was lower (p < 0.05), but was higher (p < 0.05) at 6 and 9 h in A than that in B. Truax was 3 h for both preparations. The mean Cmax (mg/100 ml, above the initial value) was 1.11 for A and 1.09 for B. The mean AUC_<0-24>(mg・h/100 ml)was 10.57 for A and 10.13 for B. The MRT_<0-24> (h) for A was 8.20 compared to 7.82 for B (p<0.05>). The MRT_<0-∞>(h) was 15.21 and 14.68 for A and B, respectively. The mean amount of vitamin C (mg, above the initial value) excreted in urine during the 0-3 h was 38 for A and 53 for B (p<0.05). During 3-6 h it was 133 and 122 (p<0.05) for A and B, respectively. The percentage of the dose excreted during the 0-24 h was essentially the same: 27.0 % for A and 26.7 % for B. The mean urinary excretion of oxalic acid (mg/24 h) following vitamin C administration was 33.7 for A and 34.8 for B, but the increase of oxalic acid was minor. In conclusion, we found that although minor differences were observed in absoption rate and residence time between A and B, calcium ascorbate and ascorbic acid show similar pharmacokinetics after oral administration.

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