Journal of Lipid Research, Vol 24, 441-448, Copyright © 1983 by Lipid Research, Inc.
Formation of fatty acid esterified vitamin D3 in rat skin by exposure to ultraviolet radiation
K Takada
The formation of fatty acid esters of vitamin D3 was demonstrated in rat
skin exposed to artificial ultraviolet rays by using multi- dimensional
high-performance liquid chromatography, ultraviolet spectrophotometry, and
gas-liquid chromatography-mass spectrometry. This result indicated that the
fatty acid esters of 7- dehydrocholesterol in rat skin (at least 80% of
7-dehydrocholesterol in rat skin is esterified) is also isomerized into
vitamin D3 ester in vivo. The initial percentage of the esterified form was
84.3% and this did not significantly change up to the time when about half
of the skin total vitamin D3 disappeared (2 days). Consequently, it was
speculated that the vitamin D3 ester was delivered into the blood
circulation from skin without having been hydrolyzed. This was supported by
the presence of vitamin D3 ester in rat plasma exposed to ultraviolet
radiation. In addition, in connection with the study of the restriction of
vitamin D3 synthesis, distribution of total vitamin D3 in rat skin exposed
to ultraviolet irradiation in vivo was compared with that in isolated skin
exposed to ultraviolet radiation. The dermal layer of the isolated skin
contained about 4 times more total vitamin D3 than that of in vivo skin.
This finding suggests not only that ultraviolet rays could not penetrate
deeply into the in vivo skin, but that the restriction of cutaneous
synthesis of vitamin D3 observed in vivo may arise from this reduced
penetration of ultraviolet rays.
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