23-25-dihydroxyvitamin-d3 and calcifediol-lactone

To elucidate the biosynthesis of 25-hydroxyvitamin D3-26,23-lactone, various vitamin D3 derivatives were incubated individually with kidney homogenates prepared from vitamin D3-supplemented chicks, a preparation known to produce the 25-hydroxyvitamin D3-26,23-lactone from 25-hydroxyvitamin D3. The 25-hydroxyvitamin D3-26, 23-lactone produced in vitro was then separated, purified, identified, and quantitated by consecutive analysis by high-pressure liquid chromatography. The naturally occurring 23(S), 25(R)-25-hydroxyvitamin D3-26,23-lactone was produced from 23(S),25-dihydroxyvitamin D3, 25(R),26-dihydroxyvitamin D3, and 23(S),25(R),26-trihydroxyvitamin D3. 23(S),25 (S)-25-Hydroxyvitamin D3-26,23-lactone was synthesized from 25(S),26-dihydroxyvitamin D3 and 23(S),25(S),26-trihydroxyvitamin D3. The relative amounts of 25-hydroxyvitamin D3-26,23-lactones generated from the following vitamin D3 derivatives used as substrate (23(S),25(S),26-trihydroxyvitamin D3; 23(R),25(R),26-trihydroxyvitamin D3; 23(S),25(R),26-trihydroxyvitamin D3; 23(R),25(S),26-trihydroxyvitamin D3; 23(S), 25-dihydroxyvitamin D3; 23(R),25-dihydroxyvitamin D3; 25(S),26-dihydroxyvitamin D3; and 25(R),26-dihydroxyvitamin D3) are, respectively, 15:1.7:24:3.3:2.5:0:1:1.7. These results indicate that when the lactonization at C-23 and C-26 positions of various vitamin D3 derivatives occurred the stereochemical configuration at their C-23 and/or C-25 positions was not changed and the difference of the stereochemical configurations determined the rate of lactonization.

Topics: Animals; Calcifediol; Calcitriol; Chickens; Chromatography, High Pressure Liquid; Dihydroxycholecalciferols; Hydroxycholecalciferols; Kidney; Male; Molecular Conformation; Stereoisomerism

Topics: Animals; Calcifediol; Chickens; Chromatography, High Pressure Liquid; Dihydroxycholecalciferols; Hydroxycholecalciferols; Kidney; Spectrophotometry, Ultraviolet

23,25-Dihydroxyvitamin D3 was isolated from vitamin D-toxic pig plasma by sequential chromatography through two gravity columns and three high performance liquid chromatography systems. Two of the high performance liquid chromatography systems separated the R and S diastereomers of 23,25-dihydroxyvitamin D3 and demonstrated that the metabolite has the 23S configuration. Ultraviolet absorbance and mass spectroscopy of the pure metabolite and mass spectroscopy of its trisilylated derivative confirmed the structural assignment. 23S,25-Dihydroxyvitamin D3, 23R,25-dihydroxyvitamin D3, 25S,26-dihydroxyvitamin D3, and 25R,26-dihydroxyvitamin D3 were assessed for their ability to produce 25-hydroxyvitamin D3-26,23-lactone in vitamin D2-toxic rats. On 23S,25-dihydroxyvitamin D3, of the naturally occurring compounds, was able to increase the plasma lactone concentration. This metabolite was a more efficient precursor than 25-hydroxyvitamin D3, suggesting that 23S-hydroxylation is a rate-limiting step in 25-hydroxyvitamin D3-26,23-lactone formation. 23S,25-Dihydroxyvitamin D3 was not detected in 25-hydroxyvitamin D3-dosed rats, indicating that the former is rapidly metabolized. Nephrectomized rats had a diminished but significant ability to synthesize 25-hydroxyvitamin D3-26,23-lactone from 25-hydroxyvitamin D3. Nephrectomy did not affect synthesis of 25-hydroxyvitamin D3-26,23-lactone from 23S,25-dihydroxyvitamin D3. These results demonstrate that vitamin D3 23S-hydroxylase(s) are also located extrarenally and that extrarenal tissues are quantitatively important to 25-hydroxyvitamin D3-26,23-lactone synthesis.

Topics: Animals; Calcifediol; Cholecalciferol; Chromatography, High Pressure Liquid; Dihydroxycholecalciferols; Ergocalciferols; Female; Hydroxycholecalciferols; Male; Mass Spectrometry; Nephrectomy; Rats; Rats, Inbred Strains; Swine

Vitamin D supplemented rats produce a metabolite of 25-hydroxy[3 alpha-3H]vitamin D3 that is easily separated from known metabolites by using high-performance liquid chromatography. The production of this metabolite in vivo as well as 1,25-dihydroxyvitamin D3, 24(R),25-dihydroxyvitamin D3, and 25-hydroxyvitamin D3 26,23-lactone is largely if not totally eliminated by nephrectomy. Kidney homogenates from vitamin D supplemented chickens incubated with 25-hydroxyvitamin D3 produce significant quantities of the new, unknown metabolite. This metabolite was isolated in pure form from such incubation mixtures by using both straight-phase and reversed-phase high-performance liquid chromatography. This metabolite has been positively identified as 23,25-dihydroxyvitamin D3 by ultraviolet absorption spectrophotometry, mass spectrometry, and derivatization. This structure was confirmed by chemical synthesis of both C-23 stereoisomers. Although the natural product exactly comigrates with one of the synthetic isomers, the exact stereochemistry of the natural product remains unknown. It is possible that this new metabolite is an intermediate in the biosynthesis of 25-hydroxyvitamin D3 26,23-lactone.

Topics: Animals; Calcifediol; Chickens; Cholecalciferol; Chromatography, High Pressure Liquid; Dihydroxycholecalciferols; Hydroxycholecalciferols; Mass Spectrometry; Nephrectomy; Rats; Spectrophotometry, Ultraviolet; Stereoisomerism