title: Influence of triamcinolone, estradiol-17 beta and testosterone on 1,25-dihydroxyvitamin D3 binding performances to its chick intestinal receptor.
abstract: We have investigated the effects of large molar excesses (20,000) of triamcinolone, estradiol-17 beta and testosterone on the binding performances of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] to its receptor. The source of receptor was a duodenal chromatin fraction of vitamin D replete chickens which exhibited a high level of positive cooperativity (Hill coefficient = 1.50 +/- 0.12; n = 4) in the binding of 1,25(OH)2D3 to the two sites of its intestinal receptor. Triamcinolone did not modify the affinity, cooperativity level and maximum binding capacity of the 1,25(OH)2D3 receptor. Estradiol-17 beta induced a slight but significant increase of 13 +/- 1% (P less than 0.01) of the receptor capacity and testosterone a 29 +/- 6% (P less than 0.02) increase of the receptor affinity. A combination of estradiol-17 beta and testosterone did not modify the 1,25(OH)2D3 receptor's binding performances. In conclusion, the effects of corticoids, estradiol-17 beta and testosterone under in vitro conditions on the 1,25(OH)2D3 receptor's binding performances were found to be marginal in our system. Other studies under in vivo conditions, possibly at the pre-transcriptional level, of these steroids effects on the 1,25(OH)2D3 receptor gene regulation expression would be of great interest.
mesh_terms: D000818:Animals; D002645:Chickens; D002843:Chromatin / Q000378:metabolism; D004386:Duodenum / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology*; D014221:Triamcinolone / Q000494:pharmacology*
chemical_list: D002843:Chromatin; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D014221:Triamcinolone; D013739:Testosterone; D004958:Estradiol