EXPOSURE OF PERIODONTAL-LIGAMENT CELLS TO METHYL MERCAPTAN REDUCES INTRACELLULAR PH AND INHIBITS CELL-MIGRATION

Volatile sulfur compounds such as hydrogen sulfide and methyl mercapta n have been associated with adult periodontitis as well as with healin g surgical wounds. To examine the effects of these compounds on the pe riodontium, we assayed periodontal ligament (PDL) cells for changes in intracellular pH, total protein, and cell migration following chronic exposure to CH3SH. Intracellular pH was quantitated by fluorescence m easurements of cells loaded with BCECF, a pH-sensitive dye. Data show that 48-hour exposure to mercaptan lowered resting intracellular pH bu t did not consistently alter activity of the Na/H exchanger. This effe ct was seen in PDL cells from three different patients. Lowered pH was accompanied by decreases in both total protein and mature alpha 1 and alpha 2 chains of type I collagen. Since reductions in intracellular pH and total protein have been associated with inhibition of cell moti lity, migration was quantitated by sequential computer imaging, which measured the increase in size of plated cell circles at different time s of migration. Incubation of PDL cells in pH 7.4 and 6.6 buffers reve rsibly altered intracellular pH. Migration was reversibly inhibited in pH 6.8 buffer. Exposure to CH3SH reduced intracellular pH in pH 7.4 b uffer and in three independent assays inhibited enlargement of cell ci rcles in pH 7.4 medium. These effects were therefore not related to al terations of extracellular pH, which remained at 7.4. The results supp ort the hypothesis that gases such as methyl mercaptan may play a role in both surgical wound healing and periodontal disease by adversely a ffecting cell function and suggest that alterations in intracellular p H may be part of the mechanism for these changes.