Okano T, Yasumura M, Mizuno K, Kobayashi T
J Nutr Sci Vitaminol (Tokyo). 1978;24(1):47-56. doi: 10.3177/jnsv.24.47.
In order to confirm the photochemical conversion of 7-dehydrocholesterol (7-DHC) into vitamin D3 in rat skin, the following in vitro and in vivo experiments were carried out. In the first (in vitro) experiment, the skin stripped off from a sacrificed normal rat was irradiated with an ultraviolet (UV) lamp for a constant period. In the second (in vivo) experiment, the normal rat, irradiated under the same condition mentioned above, was sacrificed and then the skin was stripped off. Lipids were individually extracted with chloroform-methanol (1:1) from the skin obtained in the two experiments and the solvent was evaporated. The resulting residue was saponified and the unsaponifiable matter extracted with benzene was purified by application to hydroxyalkoxy-propyl (HAP) Sephadex column chromatography. The resulting purified vitamin D3 fraction was applied to high-performance liquid chromatography (HPLC) in order to estimate vitamin D3. No peak, aside from that of alpha-naphthol as an internal standard, was observed in the HPLC chromatogram on the skin obtained from the non-irradiated rat, whereas the peak corresponding to vitamin D3 was observed in each HPLC chromatogram on both the irradiated skin (in vitro experiment) and the skin obtained from the irradiated rat (in vivo experiment). The peaks, confirmed to be due to vitamin D3 by the results of co-chromatography, were increased according to the increase of irradiation energy and there were little differences between the corresponding estimated values of vitamin D3 in the two experiments. These results prompted the conclusion that 7-DHC in rat skin was photochemically converted into vitamin D3 by UV irradiation and that the in vivo conversion mechanism might be the same as the in vitro one.
为了证实大鼠皮肤中7-脱氢胆固醇（7-DHC）向维生素D3的光化学转化，进行了以下体外和体内实验。在第一个（体外）实验中，用紫外线（UV）灯对从处死的正常大鼠身上剥离的皮肤照射一段固定时间。在第二个（体内）实验中，将在上述相同条件下照射的正常大鼠处死，然后剥离皮肤。分别用氯仿-甲醇（1:1）从两个实验中获得的皮肤中提取脂质，并蒸发溶剂。将所得残渣皂化，用苯提取的不皂化物通过应用于羟烷氧基丙基（HAP）葡聚糖凝胶柱色谱进行纯化。将所得纯化的维生素D3馏分应用于高效液相色谱（HPLC）以估算维生素D3。在从未照射大鼠获得的皮肤的HPLC色谱图中，除了作为内标的α-萘酚的峰外，未观察到其他峰，而在照射皮肤（体外实验）和从照射大鼠获得的皮肤（体内实验）的每个HPLC色谱图中均观察到对应于维生素D3的峰。通过共色谱结果证实为维生素D3的峰随着照射能量的增加而增加，并且在两个实验中维生素D3的相应估算值之间几乎没有差异。这些结果得出结论，大鼠皮肤中的7-DHC通过紫外线照射光化学转化为维生素D3，并且体内转化机制可能与体外机制相同。
