1 Alpha,25-dihydroxyvitamin D3 rapidly increases cytosolic calcium in clonal rat osteosarcoma cells lacking the vitamin D receptor.
1 alpha,25-Dihydroxyvitamin D3 [1 alpha,25-(OH)2D3] rapidly increases cytosolic calcium in a variety of cell types. Although these rapid effects do not appear to directly involve genome activation, the requirement for the classic vitamin D receptor is unclear. Clonal rat osteosarcoma cells, ROS 17/2.8, respond to 1 alpha,25-(OH)2D3 with an increase in osteocalcin message but ROS 24/1 cells do not. The lack of the receptor for vitamin D in the ROS 24/1 cells has been confirmed by the absence of any detectable vitamin D-receptor complex binding to the vitamin D-responsive element (VDRE) of the osteocalcin gene and the absence of vitamin D receptor mRNA in the cells. Quin-2-loaded ROS 17/2.8 and ROS 24/1 cells were treated with 1 alpha,25-(OH)2D3 in the presence and absence of extracellular calcium and with the inactive epimer, 1 beta,25-dihydroxyvitamin D3 [1 beta,25-(OH)2D3]. The 1 alpha,25-(OH)2D3 increased cytosolic calcium in the ROS 17/2.8 and 24/1 cells after 5 minutes in a dose-responsive manner and in the presence and absence of extracellular calcium. Pretreatment of both cell lines with 1 beta,25-(OH)2D3 for 30 s blocked the hormone-induced rise in cytosolic calcium. The rapid effects of 1 alpha,25-(OH)2D3 on ROS cells with and without the vitamin D receptor and the ability of the inactive epimer to inhibit these effects indicate that the signaling system mediating the hormone's rapid actions is not the classic vitamin D receptor.
Baran
D T
DT
Department of Medicine, University of Massachusetts Medical Center, Worcester.
Sorensen
A M
AM
Shalhoub
V
V
Owen
T
T
Oberdorf
A
A
Stein
G
G
Lian
J
J
D000634:Aminoquinolines; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002999:Clone Cells / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects* / Q000378:metabolism; D005456:Fluorescent Dyes; D009687:Nuclear Proteins / Q000302:isolation & purification; D012516:Osteosarcoma / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000032:analysis*; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014407:Tumor Cells, Cultured
D000634:Aminoquinolines; D005456:Fluorescent Dyes; D009687:Nuclear Proteins; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D002117:Calcitriol; C035739:Quin2; D002118:Calcium