Cholecalciferol 25-hydroxylation is similar in liver microsomes from male and female rats when cholecalciferol concentration is low.
We compared cholecalciferol 25-hydroxylation in liver microsomes of male and female rats. The rate of production of 25-hydroxycholecalciferol was similar in liver microsomes from female rats and those from male rats when cholecalciferol concentration ranged from 50 to 200 nmol/L. The liver cytosolic fraction stimulated the 25-hydroxylase activity of the microsomes up to 100% in both male and female rats at 44 nmol/L cholecalciferol. Cytosol metabolized cholecalciferol to a currently unidentified metabolite. At 300 nmol/L cholecalciferol, synthesis of the cytosolic metabolite was 100% greater than at 100 nmol/L and coincided with 32% lower synthesis of 25-hydroxycholecalciferol. These results suggest similar 25-hydroxy-lase activity in liver microsomes from male and female rats and similar ability of liver cytosol from these rats to stimulate 25-hydroxylation at low nanomolar concentrations of cholecalciferol, whereas inhibitory effects of cytosol at higher concentrations of cholecalciferol were shown.
Thierry-Palmer
M
M
Department of Biochemistry, Morehouse School of Medicine, Atlanta, GA 30310-1495.
Free
A L
AL
Nagappan
P R
PR
Butler
A R
AR
D000818:Animals; D002112:Calcifediol / Q000378:metabolism*; D002762:Cholecalciferol / Q000378:metabolism*; D053493:Cholestanetriol 26-Monooxygenase; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006900:Hydroxylation; D008099:Liver / Q000378:metabolism / Q000648:ultrastructure; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D013250:Steroid Hydroxylases / Q000378:metabolism*
D002762:Cholecalciferol; D013250:Steroid Hydroxylases; D053493:Cholestanetriol 26-Monooxygenase; D002112:Calcifediol