Photochemical conversion of 7-dehydrocholesterol into vitamin D3 in rat skins.

Determination of 1,25-dihydroxyvitamin D2 in rat serum using liquid chromatography with tandem mass spectrometry

“…Both vitamin D 2 and vitamin D 3 must be metabolized into their active forms before exerting their biological effects. Vitamin D 2 and vitamin D 3 undergo the same metabolic processes involving 25-hydroxlyation in the liver, followed by 1␣-hydroxylation in the kidney, to produce the biologically active metabolites 1,25(OH) 2 D 2 and 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ), respectively [6,7]. Several vitamin D 2 and vitamin D 3 analogs have been developed as therapeutic agents such as calcitriol (i.e., 1,25(OH) 2 D 3 ), paricalcitol (i.e., 19-nor-1,25(OH) 2 D 2 ), and doxercalciferol (i.e., 1␣(OH)D 2 ) to treat hyperparathyroidism in chronic kidney disease (CKD) patients.…”

“…Vitamin D 3 can be obtained from dietary intake or exposure of skin to sunlight. The UV rays of sunlight induce the photolytic conversion of 7-dehydrocholesterol (a mammalian sterol) to pro-vitamin D 3 followed by thermal isomerization to vitamin D 3 [1][2][3]. Vitamin D 2 is synthesized in a similar manner from ergosterol through sunlight exposure to pro-vitamin D 2 which rapidly isomerizes to vitamin D 2 in plant and fungi [4,5].…”

Metabolism of Orally Adiministered Ergosterol and 7-Dehydrocholesterol in Rats and Lack of Evidence for Their Vitamin D Biological Activity.

“…Therefore, the sterols are designated as provitamins D2 and D3, respectively. On the other hand, significant amounts of 7-DHC exist as an intermediate of cholesterol biosynthesis from acetyl CoA in skin of mammals (2,3) and the endogenous 7-DHC can be also coverted into vitamin D3 by UV exposure of the skin in the same manner as in a test tube (4,5) . The vitamin D3 endogenously formed in the skin is absorbed in blood and metabolized to 25 a Significantly different from control (p<0 .01).…”

Vitamin D and the vasculature: can we teach an old drug new tricks?

“…Vitamin D3, derived from the diet or by bioactivation of 7-dehydrocholesterol, is inert and must be activated to exert its biological activity. Vitamin D3 (cholecalciferol) is produced in the skin by ultraviolet-light-induced photolytic conversion of 7-dehydrocholesterol to previtamin D3 [1,2] followed by thermal isomerisation to vitamin D3 or cholecalciferol [3,4] . Thus, sun exposure is the principal source of circulating vitamin D stores and skin pigmentation is a main regulator of circulating vitamin D levels.…”