1 beta, 25 (OH)2-vitamin D3 is an antagonist of 1 alpha,25 (OH)2-vitamin D3 stimulated transcaltachia (the rapid hormonal stimulation of intestinal calcium transport).
The steroid hormone 1 alpha,25-dihydroxyvitamin-D3 [1 alpha,25(OH)2D3] stimulates biological responses via both genomic mechanisms and nongenomic mechanisms (opening of voltage-gated Ca2+ channels). We report here that 1 beta, 25(OH)2-vitamin-D3 (a) is devoid of activity as an agonist for transcaltachia, (b) is a potent stereospecific antagonist of 1 alpha,25 (OH)2D3 stimulation of the nongenomic transcaltachia response and also (c) has less than 1% the ability of 1 alpha,25(OH)2D3 to bind to the chick intestinal nuclear 1 beta,25(OH)2D3 receptor. We conclude that the membrane response element(s) which generates the nongenomic response of transcaltachia has a different ligand specificity than the classic nuclear 1 alpha, 25(OH)2D3 receptor.
Norman
A W
AW
Department of Biochemistry, University of California, Riverside 92521.
Nemere
I
I
Muralidharan
K R
KR
Okamura
W H
WH
D000818:Animals; D001667:Binding, Competitive; D002117:Calcitriol / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002645:Chickens; D004386:Duodenum / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects / Q000378:metabolism*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014807:Vitamin D / Q000494:pharmacology; D014808:Vitamin D Deficiency / Q000378:metabolism
D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D014807:Vitamin D; D002117:Calcitriol; D002118:Calcium