VITAMINS

1α, 25-Dihydroxyvitamin D_3 [1α,25 (OH)_2D_3], the most potent metabolite of vitamin D_3, is now considered to be a hormone that mediates calcium transport in target tissues such as intestine and bone. It is known that 1α, 25 (OH)_2D_3 enters the cell and associates with the specific nuclear receptor (VDR), which results in the de novo synthesis of several 1α, 25 (OH)_2D_3-dependent proteins. Recent studies have indicated that VDR is present not only in the classical target tissues of vitamin D (intestine, bone and kidney), but also in almost all tissues and cells examined. This raised a question whether 1α, 25 (OH)_2D_3 has a more subtle function in a wide variety of cells. A breakthrough in the study on 1α, 25 (OH)_2D_3 functions was made in 1981 by Abe et al., who clearly demonstrated that 1α, 25 (OH)_2D_3 induces differentiation of mouse myeloid leukemia cells (Ml) into cells of the monocyte-macrophage lineage. The differentiation-inducing activity of 1α, 25 (OH)_2D_3 has now been applied to the treatment of the skin disease, psoriasis vulgaris. In this article, the classical calcium-regulating activity of 1α, 25 (OH)_2D_3 is explained by the newly discovered differentiation-inducing activity of the vitamin, in particular focussing polyamine metabolism in intestine and osteoclast differentiation in bone.

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Non-thermal effect of ceramics radiation on xanthine oxidase activity and the inhibitory effect of the irradiated inhibitors have been investigated using the enzyme, substrate, and competitive inhibitors which were separately irradiated under cooling. K_m values in the irradiated enzyme systems of both uric acid formation and superoxide production were reduced to 57〜50% of the non-irradiated control. Their V_<max>/K_m values were increased up to 163〜170% of the non-irradiated control. The K_i values for competitive inhibitors, i. e., folic acid, 5-formyltetrahydrofolate and allopurinol, in the irradiated enzyme system of superoxide production were 23, 41 and 100% of the non-irradiated control, respectively. Although these kinetic values were variously affected by the combination of the irradiated and non-irradiated components, the enzyme reaction was greatly affected when all components of the reaction were irradiated. Spectra of the 3h-irradiated folate showed a red shift of 50 to 60 kJ/mol. This suggests the existence of the intramolecular hydrogen bonding between pterin and 4-oxo residue which might be modified by a solvent ordering effect of the ceramics radiation. A steady-state thermodynamic molecular kinetic analysis for the reaction estimated the followings : (1) the irradiated enzyme may be kept in a folding state by such an entropy effect as a decrease or negative mode, (2) the formation of Michaelis complex has been accelerated, (3) the activated complex has been stabilized, (4) a solvation or an electro-striction with water of xanthine, folates and the active center of the enzyme may be promoted by irradiating the components in aqueous solution. These results suggest that the ceramics radiation has caused the regulation of the enzyme activity and the modification of the folate structure in aqueous solution through the solvent ordering effect.

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We previously measured the values of vitamin C in 122 kinds of vegetables and fruits in their golden season (Vitamins, 64 : 27-35, 1990). Since the results suggest that the vitamin C contents showed great variations among seasons, we have studied seasonal changes in the contents of vitamin C and other nutrients in the samples to clarify the difference between those in their golden and poor seasons. Potatoes, pumpkins, cabbages, garden peas, celerys, tomatos, carrots, sweet peppers, broccolies, spinaches, kiwifruits and mangos were chosen as the samples in this study, because they are very popular and selling for long periods in markets. The samples were bought every month form the five markets in the department stores and super-markets in Tokyo. The contents of water, minerals (Ca, P, Fe, Na and K) and vitamins (β-carotene, niacin and vitamin C) in the samples were measured and the monthly changes among the values of the respective samples were compared each other and the results are described in this paper.

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Pharmacokinetics and bioavailability of 2 multivitamin preparations including B_1, B_6, B_<12> and/or E were studied in human male volunteers. The same dosage of 100 mg thiamine tetrahydrofurfuryl disulfide (B_1) was included in both preparations. However, one preparation (Alinamin EX^<(R)>) included high amounts of 100 mg pyridoxine hydrochloride (B_6), 1500 μg hydroxocobalamin (B_<12>) and 100 mg d, l-α-tocopherol succinate (E). The other (Alinamin A50^<(R)>) included 10 mg riboflavin (B_2), 10 mg pyridoxine hydrochloride (B_6), 20 μg cyanocobalamin (B_<12>). the results were as follows : 1) B_1 : No difference was observed between AUC of both preparations. T_<max> tended faster in Alinamin EX^<(R)>. 2) B_6 : AUC by administration of Alinamin EX^<(R)> was 9 times larger than in Alinamin A50^<(R)>. 3) B_<12> : AUC by administration of Alinamin EX^<(R)> was 4 times larger than in Alinamin A50^<(R)>. 4) E : A significant increase in plasma was observed by administration of Alinamin EX^<(R)>. AUC represents the area under curve obtained from the blood drug concentration of the time course.

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