title: The existence of 25-hydroxyvitamin D3-1 alpha-hydroxylase in the liver of carp and bastard halibut.
abstract: We have found that carp and bastard halibut contain 25-hydroxyvitamin D3 (25-D3)-1 alpha-hydroxylase in the liver besides in the kidney by the following in vivo and in vitro experiments. When [3H]-25-D3 was intraperitoneally injected to vitamin D(D)-deficient carp and normal bastard halibut (D-deficient bastard halibut could not be raised because they died during farming), the profiles of high-performance liquid chromatography (HPLC) of the plasma lipid extract showed the formation of a peak corresponding to [3H]-1 alpha,25-dihydroxyvitamin D3 (1,25-D3). When [3H]-25-D3 was incubated with liver homogenates of the fish, a peak corresponding to [3H]-1,25-D3 was also observed in the profile of HPLC. The formation of the metabolite was confirmed by the thermal isomerization into the pre-isomer and mass fragmentography. Although the 1 alpha-hydroxylase was also observed in the kidney, the activity of the enzyme was lower than that in the liver. The results suggest that 25-D3-1 alpha-hydroxylase exists in the liver of carp and bastard halibut and the 25-D3 formed from D3 in the liver is immediately metabolized into 1,25-D3 in the same tissue. The suggestion is supported by the fact that D3 is a major circulating compound with small amounts of 1,25-D3 in the fish while the plasma levels of 25-D3 are under the limit of detection.
authors.affiliation: Department of Hygienic Sciences, Kobe Women's College of Pharmacy, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Takeuchi
authors.forename: T
authors.initials: T
authors.lastname: Okano
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3 / Q000097:blood; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000378:metabolism*; D000818:Animals; D002112:Calcifediol / Q000008:administration & dosage / Q000097:blood; D002347:Carps / Q000378:metabolism*; D002762:Cholecalciferol / Q000008:administration & dosage / Q000097:blood; D053493:Cholestanetriol 26-Monooxygenase; D002851:Chromatography, High Pressure Liquid; D005399:Fishes / Q000378:metabolism*; D007274:Injections, Intraperitoneal; D007668:Kidney / Q000201:enzymology / Q000648:ultrastructure; D008099:Liver / Q000201:enzymology* / Q000648:ultrastructure; D008928:Mitochondria / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D013250:Steroid Hydroxylases / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D014316:Tritium; D014808:Vitamin D Deficiency / Q000097:blood / Q000201:enzymology
chemical_list: D014316:Tritium; D002762:Cholecalciferol; D015650:24,25-Dihydroxyvitamin D 3; D013250:Steroid Hydroxylases; D053493:Cholestanetriol 26-Monooxygenase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002112:Calcifediol