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Conversion of 25-Hydroxyvitamin D 3 . To 1, 25-Dihydroxyvitamin D 3 and 24,25-Dihydroxyvitamin D 3 in Renal Slices from the Rat

1981; Oxford University Press; Volume: 109; Issue: 1 Linguagem: Inglês

10.1210/endo-109-1-218

1945-7170

H. J. Armbrecht, Terry V. Zenser, Bernard B. Davis,

Electrolyte and hormonal disorders

Isolated renal cortical slices were used to study the conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and 24,25-dihydroxyvitamin D3 [24, 25- (OH)2D3] by the rat kidney. Production of 1, 25-(OH)2D3 and 24,25-(OH)2D3 was linear with time (30–90 min) and tissue weight (40–250 mg). Production of 1, 25-(OH)2D3 was greatest (134 ± 17 pg/mg tissue.h) in animals fed a low calcium, vitamin D-deficient diet. The greatest 24, 25-(OH)2D3 production (106 ± 17 pg/mg tissue-h) was seen in animals fed a high calcium, vitamin D-replete diet. 1, 25-(OH)2D3 production was reduced to 23% of maximum by the addition of 1.2% calcium or strontium to the vitamin D-deficient, low calcium diet. Production of 1, 25-(OH)2D3 and 24,25-(OH)2D3 was greatly reduced in renal cortical slices that had been heated before incubation. Slices of renal medulla produced only small amounts of 1, 25- (OH)2D3 compared to slices of renal cortex. These studies provide direct evidence for the production of 1, 25-(OH)2D3 and 24,25-(OH)2D3 by the mammalian renal cortex. They also demonstrate that this production may be modulated by dietary calcium, strontium, and vitamin D.