Fluoride rapidly and transiently raises intracellular calcium in human osteoblasts.
We examined the effect of fluoride (F) on intracellular ionic calcium [Ca2+]i in normal human osteoblasts maintained in culture. Cells were grown on glass coverslips to near-confluency and loaded with the Ca-sensitive dye, fura-2AM. Fluorescence changes were monitored in single cells using an inverted microscope coupled by fiberoptic to a microspectrofluorometer. The addition of F (100 ng/mL) to the medium promoted a rapid and significant increase in free [Ca2+]i from a resting level of 245 +/- 36 SE nM to a peak concentration of 440 +/- 51 nM (p less than 0.04). This increase in [Ca2+]i began at 10-20 s after addition of F and was maximal by 30 s. Intracellular [Ca2+]i levels then returned to near resting values by 60-80 s after F addition. This response was evident with as little as 25 ng/ml of fluoride and was dose dependent up to 500 ng/ml. At concentrations greater than 500 ng/ml, there appeared to be an attenuation of the rise in [Ca2+]i. The observed rise in [Ca2+]i was dependent on extracellular calcium since lowering extracellular calcium concentration or incubation with calcium channel blockers abolished the response. This observation supports a role of increased [Ca2+]i as one of the initial events of fluoride on action osteoblasts.
Zerwekh
J E
JE
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
Morris
A C
AC
Padalino
P K
PK
Gottschalk
F
F
Pak
C Y
CY
D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004110:Diltiazem / Q000494:pharmacology; D005456:Fluorescent Dyes; D005459:Fluorides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D016257:Fura-2 / Q000031:analogs & derivatives*; D006801:Humans; D009543:Nifedipine / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
D001572:Benzofurans; D005456:Fluorescent Dyes; D010281:Parathyroid Hormone; C049925:fura-2-am; D014700:Verapamil; D004110:Diltiazem; D009543:Nifedipine; D005459:Fluorides; D002118:Calcium; D016257:Fura-2