Synthesis of 25-hydroxyvitamin D3-26,23-lactone but not 24,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3 in opossum kidney cells treated with 1 alpha, 25-dihydroxyvitamin D3.
The pathway from 25-hydroxyvitamin D3(25[OH]D3) to 25-hydroxyvitamin D3-26,23-lactone (25[OH]D3-26,23-lactone) is important in the renal degradation of vitamin D metabolites. Our objective was to investigate the regulation of 25(OH)D3 metabolism in the opossum kidney (OK) cell line which has been used for studying the actions of the calcium-regulating hormones. While the untreated OK cells did not produce 25(OH)D3 metabolites, the synthesis of the lactone was increased dose-dependently by 20h pretreatment with 1 alpha,25-dihydroxyvitamin D3 (1,25[OH]2D3), peaked at 10(-7) M 1,25(OH)2D3, and decreased with higher concentrations. Little production of 24,25-dihydroxyvitamin D3 (24,25[OH]2D3) was observed after any dose of 1,25(OH)2D3. The increase in the production of lactone induced by 10(-7) M 1,25(OH)2D3 was detectable at 2 h, peaked between 4 and 24 h, and decreased gradually until 48 h. Its induction was inhibited by actinomycin D and cycloheximide, suggesting that de novo protein synthesis is required for such induction. After treatment with 10(-7) M 1,25(OH)2D3 for 20 h, 24-hydroxylase (24-OHase) mRNA was not detected in OK cells, but was found evident in COS-7 cells (a renal cell line). Moreover, the COS-7 cells treated with 10(-7) M 1,25(OH)2D3 metabolized 25(OH)D3 to 24,25(OH)2D3. These results indicate that 1,25(OH)2D3 stimulates the synthesis of 25(OH)D3-26,23-lactone in a dose- and time-dependent manner, but does not induce the gene expression or activity of 24-OHase in OK cells.
Horiuchi
N
N
Department of Biochemistry, Ohu University School of Dentistry, Koriyama, Japan.
Saikatsu
S
S
Akeno
N
N
Abe
M
M
Kimura
S
S
Yamada
S
S
D015650:24,25-Dihydroxyvitamin D 3 / Q000096:biosynthesis*; D000818:Animals; D002112:Calcifediol / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D002460:Cell Line / Q000201:enzymology; D002522:Chlorocebus aethiops; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D005260:Female; D007668:Kidney / Q000166:cytology; D009893:Opossums; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D013250:Steroid Hydroxylases / Q000235:genetics; D013997:Time Factors; D065668:Vitamin D3 24-Hydroxylase
D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D015650:24,25-Dihydroxyvitamin D 3; C026396:calcifediol lactone; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D002117:Calcitriol; D002112:Calcifediol