Phenytoin-Induced Elevation of the Intracellular Calcium Concentration by Stimulation of Calcium-Sensing Receptors in Gingival Fibroblasts

Toshimi Hattori, Keisuke Nakano, Toshiyuki Kawakami

Department of Dental Pharmacology, Matsumoto Dental University, Shiojiri, Japan.
Hard Tissue Pathology Unit, Institute of Oral Science, Matsumoto Dental University, Shiojiri, Japan..

DOI: 10.4236/pp.2013.42037                

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.

Keywords

Phenytoin; Calcium-Sensing Receptor; Endoplasmic Reticulum; Gingival Fibroblast; Gingival Overgrowth

Conflicts of Interest

The authors declare no conflicts of interest.

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