VITAMINS

Germfree animals are thought to be an useful tool to establish a primary vitamin K (K) deficient model not caused by K antagonists or antibiotics treatment, because of their lack of intestinal flora. By an improvement of dietary oil source as short as 8 days feeding, severe K deficient symptoms were occurred in Germfree-K-deficient diet fed group only, whereas not at all in Conventional-K-deficient one. From the HPLC analysis of MK-4 content in liver, it was suspected that the content of MK-4 which had been thought to be an important form of K was not necessarily paralleled with the degree of K deficiency. This tendency was also observed in case of sodium latamoxef-treated mice, i.e., the hepatic content of MK-6 rather than MK-4 might reflect the degree of K deficiency. It was shown that the administered MK-4 into the colon or cecum was actually absorbed, and the curable effect of MK-4 administration on K deficiency was confirmed by the results of hepatic PIVKA-II analysis and PT or APTT measurements.

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Plasma contains two B_<12> binding proteins, R-binder (R) and transcobalamin (Tc) II. Their physiological functions are not well defined. In this study based on the known lack of species specificity with these binders, R was purified from desiccated hog stomach mucosa and Tc-II from human plasma Cohn fraction III using affinity chromatography. These proteins were complexed with [^<57>Co] B_<12> and given to rats i.v. and organ distribution was measured 5min. later. More than 90% of radioactivity was recovered from the liver when R-B_<12> was given, but it was significantly reduced if rats were pretreated with intravenous asialofetuin; the reduction was minimal with fetuin treatment. Tc-II-B_<12> was distributed more evenly among organs and uptake by the liver was not inhibited by asialofetuin. Hepatic parenchymal cells were separated by collagenase perfusion and density gradient using metrizamide, and in vitro uptake of R-and Tc-II-B_<12> by these cells was studied. Uptake of R-B_<12> was also inhibited by coexistent asialofetuin and asialomucin, but the uptake of Tc-II-B_<12> was not. These results suggest that R belongs to the group of asialoglycoproteins which is taken up by its specific receptor, asialoglycoprotein receptor, whereas Tc-II has a different system for uptake which perhaps involves another specific receptor.

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Effects of menaquinone (MK)-4 and -7 were examined using human hepatoma cell line (huH-2), which produced PIVKA-II in the culture medium. The production of PIVKA-II increased in a time- and cell concentration- dependent fashion. As vitamin K was added to the culture medium, the production of PIVKA-II decreased in parallel with increasing vitamin K concentrations. Although no changes were shown in F-II RAG fraction after the addition of vitamin K, the F-II RAG fraction became to have a coagulant activity. Accordingly, when effects of the vitamin K derivatives, MK-4 and -7, were examined on the basis of the decrease rate of PIVKA-II fraction in the huH-2 cell line, MK-7 was found to have a greater effect as compared with MK-4.

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Effects of oral administration of three kinds of B-vitamin preparation, including 1.65mg of pyridoxine (PN), and multivitamin preparation, including 7.41mg of PN and 75mg of nicotinamide (NiA-NH_2), were studied in healthy young male adults (n=5) on blood total vitamin B_6 and nicotinic acid (NiA) levels, as well as urinary excretion. (1) When a 1.65mg of PN was once orally administered after breakfast, the elevation of blood vitamin B_6 levels were 3.1 times of baseline levels after one hour, and then 22.9% of PN given were excreted as a form of 4-pyridoxic acid (PIC) in 24 hours. When 7.41mg of PN were given, the elevation of blood vitamin B_6 levels were 8.5 times of baseline levels and the 27.4% of administered dose was excreted. (2) When a 7.4mg of PN was daily administered during 7 days, the daily elevation of blood vitamin B_6 levels was calculated by the areas under the blood vitamin B_6 curve for 24 hours after administration. The areas after the 7th day's administration was 2.2 times higher than those after the 1st day's administration. Urinary excretion of PIC and its metabolites increased immediately after administration and then reached a maximum level in the 2nd day, the levels being in plateau thereafter. (3) When 75mg of NiA-NH_2 were daily administered during the same period, the areas surrounded with blood total NiA curve and the baseline at the 7th days' administration was 24.6% lower than that of the 1st day. Contrarily, urinary MNA excretion increased from 18.7% of the administered dose at the 1st day to 23.6% at the 7th day. This indicates that the metabolic turnover of NiA was accelerated by repeated administration of NiA-NH_2.

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