THE PRESENCE OF VITAMIN-D PRECURSORS IN HUMAN EPIDERMIS

[摘要] Separated epidermis, dermis, and subcutaneous fat were examined separately for total lipids, 7-dehydrocholesterol (pro-vitamin D3), cholesterol, and cholesterol esters. On the average, the 7-dehydrocholesterol content of epidermal lipids was 12 times as great as that of dermal lipids. Moreover, in epidermal lipids, 7-dehydrocholesterol accounted, on the average, for 3.7% of total sterols, compared to 1.6% for dermal lipids. Inasmuch as a major source of 7-dehydrocholesterol in human skin is within the epidermis, it appears that in man, perhaps unlike lower animals, it is not necessary to postulate that vitamin D is formed on the skin surface from where it is subsequently resorbed.