Effect of 1,25-dihydroxyvitamin D3 on cytosolic calcium in dispersed parathyroid cells.
We examined the effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on cytosolic calcium ([Ca]i) of dispersed bovine parathyroid cells, using the fluorescent dye indo-1. The addition of 10(-8) M 1,25-(OH)2D3 caused an increase in [Ca]i by 23.4 +/- 2.7% over a 10 minute period. There was a significant increase in [Ca]i within two minutes of the addition of 1,25-(OH)2D3. 1,25-(OH)2D3 increased [Ca]i in a dose-dependent manner and this occurred with as little as 10(-10) M. Neither 10(-7) M 25-(OH)D3 nor 10(-7) M 24, 25-(OH)2D3 caused a significant increase in [Ca]i. Chelation of extracellular calcium with EGTA blocked the 1,25-(OH)2D3-induced increase in [Ca]i, suggesting that the increase was mainly from extracellular calcium. Neither 10(-5) M verapamil nor 10(-4) M diltiazem blocked the 1,25-(OH)2D3-induced increase in [Ca]i. The present data suggest that 1,25-(OH)2D3 might modify membrane permeability to calcium independent of voltage-dependent calcium channels sensitive to verapamil or diltiazem. The rapid effect of 1,25-(OH)2D3 raises the possibility that its mechanism is independent of genome activation, perhaps attributable to direct interaction with components of the parathyroid cell plasma membrane.
Sugimoto
T
T
Department of Medicine, Washington University School of Medicine, St. Louis Missouri.
Ritter
C
C
Ried
I
I
Morrissey
J
J
Slatopolsky
E
E
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D003600:Cytosol / Q000378:metabolism*; D004110:Diltiazem / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000627:therapeutic use; D010280:Parathyroid Glands / Q000187:drug effects / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
D007211:Indoles; D014700:Verapamil; D004110:Diltiazem; D002117:Calcitriol; D002118:Calcium