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Updated: Aug 22, 2026
Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
Published on: September 7, 2013
Effect of u.v. rays on 7-dehydrocholesterol content in rat skin
Abstract:
Long-term exposure of rat to ultraviolet irradiation affected the cholesterol metabolism in the skin. The 7-dehydrocholesterol content was increased to 1.6 times of non-irradiated rat. However, the cholesterol content was not altered. Ultraviolet-induced precholecalciferol and cholecalciferol bound with an activator protein of delta 5,7 sterol-delta 7-reductase. This observation suggested that precholecalciferol and cholecalciferol bound with an activator protein of delta 5,7 sterol-delta 7-reductase. This observation suggested that precholecalciferol and cholecalciferol inhibit the conversion of 7-dehydrocholesterol to cholesterol and accumulate 7-dehydrocholesterol. The action of ultraviolet rays on the cholesterol metabolism in the skin may be explained as the action of ultraviolet-induced precholecalciferol and cholecalciferol.
Related Concept Videos
01:23Role of Skin in Vitamin D Synthesis
The solar UV B rays (290-315 nm) are absorbed by the skin, and 7-dehydrocholesterol (provitamin D3) photolyzes it to previtamin D3, which undergoes a rapid transformation to vitamin D3(cholecalciferol).
01:19Pigmentation
Melanin occurs in two primary forms: eumelanin that provides black and brown pigment and pheomelanin that provides red color. Dark-skinned individuals produce more melanin than those with pale...