TITLE:
Phenytoin-Induced Elevation of the Intracellular Calcium Concentration by Stimulation of Calcium-Sensing Receptors in Gingival Fibroblasts
AUTHORS:
Toshimi Hattori, Keisuke Nakano, Toshiyuki Kawakami
KEYWORDS:
Phenytoin; Calcium-Sensing Receptor; Endoplasmic Reticulum; Gingival Fibroblast; Gingival Overgrowth
JOURNAL NAME:
Pharmacology & Pharmacy,
Vol.4 No.2,
April
29,
2013
ABSTRACT: Background:The
mechanism concerning gingival overgrowth as a side effect of phenytoin, a
therapeutic drug for epilepsy has been still unclear. As one of mechanisms, by
measuring the intracellular calcium concentration ([Ca2+]i)
of the gingival fibroblasts, it has been advocated that there is relationship
between gingival overgrowth and phenytoin-induced alterations in the [Ca2+]i
in gingival fibroblasts. To confirm that phenytoin elevates the [Ca2+]i,
and if so, to find out its mode of action. Methods: The [Ca2+]i was measured with the Ca2+-sensitive
fluorescent dye fura-2/AM. Cells were soaked in a flexiperm chamber and
perfused by a saline. Drugs at appropriate concentrations were added to the perfusate. Results: Phenytoin concentration-dependently elevated the [Ca2+]i.
NPS2390, a calcium-sensing receptor (CaSR)
blocker, significantly suppressed the phenytoin-induced [Ca2+]i
elevation. U73122, a phospholipase C (PLC) inhibitor, inihibited the
phenytoin-induced [Ca2+]i elevation. TMB-8, a blocker of inositol
triphophate (IP3) receptors in ER, significantly depressed the
phenytoin-induced [Ca2+]i elevation. m-3M3FBS, a PLC activator, enhanced the phenytoin-induced [Ca2+]i
elevation. From the findings obtained, it is discussed as follows: The Ca2+-free saline and NPS2390, a
CaSR antagonist, inhibited the phenytoin-induced [Ca2+]i rise; These
results indicate that CaSRs exist in gingival fibroblasts and that CaSRs are involved
in the phenytoin-induced [Ca2+]i rise; U73122 and TMB-8 depressed
the phenytoin-induced [Ca2+]i
elevation and furthermore, m-3M3FBS
enhanced the phenytoin-induced [Ca2+]i elevation, showing that the
Ca2+ release from the ER is involved in the phenytoin-induced [Ca2+]i
elevation. Conclusion: We have concluded that phenytoin elevates the [Ca2+]i
by activating CaSRs and enhancing the Ca2+ release from the Ca2+ stores in gingival fibroblasts.