title: Stimulatory effect of testosterone on renal 25-hydroxyvitamin D-3 1 alpha-hydroxylase in guinea pig.
abstract: Castration of male guinea pigs reduced the activity of the renal mitochondrial 25-hydroxyvitamin D-3 1 alpha-hydroxylase by about 50% without affecting the apparent Km for the reaction. Testosterone substitution for 10 days after castration increased the activity to about the same level as that of sham-operated animals. Ovariectomy of female guinea pigs had no effect on the 1 alpha-hydroxylase activity. Administration of testosterone to ovariectomized female guinea pigs increased the activity by about 50%, again without affecting the apparent Km. The different manipulations had no significant effect on circulating levels of 1,25-dihydroxyvitamin D or vitamin D-binding protein (DBP). It is concluded that testosterone may be a regulator of the 25-hydroxyvitamin D-3 1 alpha-hydroxylase in guinea pigs.
authors.affiliation: Department of Clinical Chemistry, Huddinge Hospital, Sweden.
authors.forename: Y
authors.initials: Y
authors.lastname: Hagenfeldt
authors.forename: H
authors.initials: H
authors.lastname: Eriksson
authors.forename: I
authors.initials: I
authors.lastname: Björkhem
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000097:blood; D053493:Cholestanetriol 26-Monooxygenase; D005260:Female; D006168:Guinea Pigs; D007668:Kidney / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D009919:Orchiectomy; D010052:Ovariectomy; D012727:Sex Characteristics; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology*; D014809:Vitamin D-Binding Protein / Q000097:blood
chemical_list: D014809:Vitamin D-Binding Protein; D013739:Testosterone; D013250:Steroid Hydroxylases; D053493:Cholestanetriol 26-Monooxygenase; D002117:Calcitriol