Calciferols vitamin 25-hydroxycholecalciferol

The term vitamin D is used for a range of compounds which possess the property of preventing or curing rickets. They include ergocalciferol (calciferol, vitamin D ), chole-calciferol (vitamin Dg), dihydrotachysterol, alfacalcidol (la-hydroxycholecalciferol) and calcitriol (1,25-dihydroxycholecalciferol). 

Physiological forms of vitamin D include vitamin D2 (calciferol, ergocalciferol), vitamin D3 (cholecalciferol), phosphate esters of D2, D3, 25-hydroxycholecalciferol, 1,25-dihydroxycholecalciferol, and 5,25-dihydroxychole-calciferol. Vitamins D2 and D3 are 9,10-secosteroids that differ stmcturally in the degree of saturation of an... 

Vitamin D preparations that are available include er-gocalciferol (also termed calciferol, or vitamin D2), cholecalciferol (vitamin D3), alfa-calcidol (la-hydroxycholecalciferol) and calcitriol (1,25-hydroxycholcalciferol). 

Cholecalciferol 25-hydroxylase is not restricted to the liver kidneys, skin, and gut microsomes also have a cytochrome P450 -dependent enzyme that catalyzes the 25-hydroxylation of cholecalciferol and la-hydroxycholecalciferol, hut not ergocalciferol. Although there is some evidence that calcitriol can reduce the activity of calciferol 25-hydroxylase, it is not known whether this is physiologically important the major factor controlling 25-hydroxylation is the rate of uptake of cholecalciferol into the liver. It is the fate of calcidiol in the kidneys that provides the most important regulation of vitamin D metabolism (Wikvall, 2001). 

Nomenclature. Vitamin D all steroids with chole-calciferol-like biological activity cholecalciferol (vitamin D3) 25-hydroxycholecalciferol (calcidiol) la,25-dihydroxycholecalciferol (calcitriol). 

Corvol, M.T., Garabedian, M., Du Bois, M.B., et al. 1978. Vitamin D and cartilage. 11. Biological activity of 25-hydroxycholecalciferol and 24,25- and 1,25-dihydroxychole-calciferols on cultured growth plate chondrocytes. Endocrinology 102 1269-74. 

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