Short-term regulation of the renal vitamin D receptor in rats by 1,25-dihydroxycholecalciferol is calcium insensitive.
Acute regulation of the vitamin D receptor in kidney by 1,25-dihydroxycholecalciferol and dietary calcium was investigated using vitamin D-deficient rats. 1,25-Dihydroxycholecalciferol administered to normocalcemic, vitamin D-deficient rats increased the renal receptor level, whereas serum calcium and phosphorus concentrations remained nearly constant. In hypocalcemic, vitamin D-deficient rats, 1,25-dihydroxycholecalciferol caused a sharp response at 4 h, which remained elevated for the remaining 20 h. Serum calcium rose gradually over 24 h, whereas serum phosphorus remained fairly constant. When hypocalcemic, vitamin D-deficient rats were fed a high calcium diet following 14 h without food, the serum calcium concentration increased and serum phosphorus concentration decreased, whereas renal receptor levels were unchanged. These data indicate that 1,25-dihydroxycholecalciferol rapidly regulates the renal vitamin D receptor, independent of serum calcium and phosphorus, but requires an adequate serum calcium concentration to sustain a prolonged effect.
Uhland-Smith
A
A
Department of Biochemistry, University of Wisconsin-Madison, College of Agricultural and Life Sciences 53706.
DeLuca
H F
HF
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000097:blood / Q000494:pharmacology*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010758:Phosphorus / Q000097:blood; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000378:metabolism
D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D010758:Phosphorus; D002117:Calcitriol; D002118:Calcium