Author(s)

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..

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.

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

Hattori, T. , Nakano, K. and Kawakami, T. (2013) Phenytoin-Induced Elevation of the Intracellular Calcium Concentration by Stimulation of Calcium-Sensing Receptors in Gingival Fibroblasts. Pharmacology & Pharmacy, 4, 261-265. doi: 10.4236/pp.2013.42037.