title: Interactions between calciotropic hormones.
abstract: The metatarsal cytochemical bioassay (CBA) for parathyroid hormone (PTH) was adapted to study interactions between PTH and certain vitamin D metabolites. Thus, while they had no effect in the system alone, both 1,25(OH)2D3 and 25(OH)D3 caused a dose-dependent potentiation of PTH-stimulated glucose 6-phosphate dehydrogenase activity in the hypertrophic chondrocytes of the rat metatarsal. 1,25(OH)2D3 was about 1000 times more potent than 25(OH)D3. Specificity is indicated by the lack of a similar effect when either oestradiol or 1,24,25(OH)3D3 or a lactone derivative of 1,25(OH)2D3 was used. Furthermore, the rapidity of the effect of 1,25(OH)2D3 and 25(OH)D3, within 8 minutes, favours a membranophilic mechanism rather than the conventional nuclear mechanism of steroid hormone action.
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3; D000818:Animals; D001681:Biological Assay; D002112:Calcifediol / Q000378:metabolism; D002117:Calcitriol / Q000031:analogs & derivatives / Q000378:metabolism; D004100:Dihydroxycholecalciferols / Q000378:metabolism; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000378:metabolism; D008684:Metatarsus / Q000378:metabolism; D010281:Parathyroid Hormone / Q000378:metabolism*; D051381:Rats; D014807:Vitamin D / Q000378:metabolism*
chemical_list: D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D010281:Parathyroid Hormone; D014807:Vitamin D; D015650:24,25-Dihydroxyvitamin D 3; C013721:1,24,25-trihydroxyvitamin D3; C026947:1,25-dihydroxyvitamin D3-26,23-lactone; D002117:Calcitriol; D002112:Calcifediol