title: Antagonistic activity of 24-oxa-analogs of vitamin D.
abstract: 24-Oxa-vitamin D3 (24-oxa-D3) and 24-oxa-1 alpha-hydroxyvitamin D3 were designed as possible inhibitors of the vitamin D metabolic activation pathway. Their affinity for the vitamin D receptor (from pig intestine) and human vitamin binding protein were reduced, and their potency to induce cell differentiation of human leukemia cells (HL 60) or osteosarcoma cells (MG 63) was markedly reduced (19% and 3%, respectively), in comparison with calcitriol. A single or chronic injection of 24-oxa-D3 had no biological activity, whereas chronic administration of 24-oxa-1 alpha-hydroxy-D3 showed weak agonist activity in rachitic chicks. When the 24-oxa-D3 was given prior to a single injection of vitamin D3, lower values of serum calcium (64% of the value obtained in vitamin D-treated animals), osteocalcin (52%), 25-(OH)D3 (45%) and duodenal calbindin-D 28K (9.4%) were found. When given chronically in a 100-fold more excess no clear antagonistic effects were observed. 24-Oxa-D3 is thus a new metabolic weak antagonist of vitamin D3, but adding a hydroxyl group at C-1 creates a weak agonist.
authors.affiliation: Laboratorium voor Experimentele Geneeskunde en Endocrinologie, K.U. Leuven, Onderwijs en Navorsing Gasthuisberg, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Allewaert
authors.forename: L A
authors.initials: LA
authors.lastname: Sarandeses
authors.forename: A
authors.initials: A
authors.lastname: Mourino
authors.forename: R
authors.initials: R
authors.lastname: Convents
authors.forename: B K
authors.initials: BK
authors.lastname: Tan
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: R
authors.initials: R
authors.lastname: Bouillon
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D002118:Calcium / Q000097:blood; D002454:Cell Differentiation / Q000187:drug effects; D002645:Chickens; D002762:Cholecalciferol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute; D012516:Osteosarcoma; D018167:Receptors, Calcitriol / Q000378:metabolism; D013552:Swine; D014407:Tumor Cells, Cultured; D014807:Vitamin D / Q000037:antagonists & inhibitors*; D014809:Vitamin D-Binding Protein / Q000378:metabolism
chemical_list: C095630:24-oxa-1-hydroxyvitamin D3; C095629:24-oxavitamin D3; D018167:Receptors, Calcitriol; D014809:Vitamin D-Binding Protein; D014807:Vitamin D; D002762:Cholecalciferol; D002117:Calcitriol; D002118:Calcium