title: Certain vitamin D metabolites potentiate the expression of parathyroid hormone bioactivity.
abstract: With the development of a sensitive bioassay for the skeletal effects of parathyroid hormone (PTH), it has become possible to investigate the possible interaction between PTH and vitamin D3 metabolites. This assay is based on the stimulation of glucose-6-phosphate dehydrogenase (G6PD) activity in either the hypertrophic chondrocytes of the growth plate or the osteoblasts lining the metaphyseal trabeculae of rat metatarsals. The response to PTH is paralleled by the activity of dibutyryl cAMP. None of the vitamin D3 metabolites tested had any effect on enzyme activity when tested by themselves. However, both 1,25(OH)2D3 and 25(OH)D3 caused a dose-related potentiation of the response to PTH. Neither 1,24,25(OH)3D3 nor 1,25(OH)2D3 26,23-lactone potentiated the response to PTH. Because this potentiation of the response to PTH occurs after only 8 minutes, it is suggested that it represents a nongenomic response to the vitamin D3 metabolites.
authors.affiliation: Division of Cellular Biology, Kennedy Institute, London, UK.
authors.forename: J N
authors.initials: JN
authors.lastname: Bradbeer
authors.forename: S
authors.initials: S
authors.lastname: Mehdizadeh
authors.forename: L J
authors.initials: LJ
authors.lastname: Fraher
authors.forename: N
authors.initials: N
authors.lastname: Loveridge
mesh_terms: D000818:Animals; D002356:Cartilage / Q000187:drug effects / Q000201:enzymology*; D002762:Cholecalciferol / Q000494:pharmacology*; D004347:Drug Interactions; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism*; D006132:Growth Plate / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D051381:Rats; D012016:Reference Values; D013329:Structure-Activity Relationship
chemical_list: D010281:Parathyroid Hormone; D002762:Cholecalciferol; D005954:Glucosephosphate Dehydrogenase