Induction of a low voltage-activated, fast-inactivating Ca2+ channel in cultured bone marrow stromal cells by dexamethasone.
The production of biochemical markers associated with the osteoblastic phenotype, and accompanying changes in the expression of voltage-operated Ca2+ channels, have been examined in rat bone marrow stromal cell cultures treated with dexamethasone (10(-8) M). Whole cell clamp analysis of voltage-operated Ca2+ channels in control cultures (using Ba2+ as the charge carrier) revealed primarily a high voltage-activated (HVA), slowly inactivating current, which was enhanced two- to threefold by treatment of the cells with Bay K 8644 (300 nM) and inhibited by nifedipine (4 microM). In dexamethasone-treated cultures, the I-V relationship for inward current was shifted to more positive potentials in comparison with control cells. Most cells in these cultures possessed both the HVA current and also a faster inactivating, low-voltage-activated (LVA), nifedipine-resistant current. These two currents could be separated both by nifedipine and by the use of steady state inactivation of the LVA current. The two components of the Ba2+ current varied widely in their relative size. The combination of LVA and HVA currents seen in dex-induced stromal cells resembles records of voltage-operated Ca2+ channels from cultures of calvarial osteoblasts.
Publicover
S J
SJ
School of Biological Sciences, University of Birmingham, Edgbaston, UK.
Thomas
G P
GP
el Haj
A J
AJ
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000032:analysis; D000818:Animals; D001853:Bone Marrow / Q000737:chemistry / Q000502:physiology*; D001854:Bone Marrow Cells; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D003094:Collagen / Q000032:analysis / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004558:Electric Stimulation; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010006:Osteoblasts / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D010641:Phenotype; D051381:Rats; D017208:Rats, Wistar
D015220:Calcium Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D003907:Dexamethasone; D003094:Collagen; D000469:Alkaline Phosphatase; D009543:Nifedipine