Studies on biochemical mechanisms of dental materials-elicited cellular toxicity

本研究旨在利用JTC-12、肾来源的MDCK和牙周膜来源的PL细胞的多项生化指标，阐明根管消毒剂甲醛的主要成分甲醛的作用机制。甲醛可引起乳酸脱氢酶漏出，并呈浓度和时间依赖性地抑制中性红摄取和四甲基偶氮唑蓝的还原。作为中性红摄取的指标，检测方法灵敏的顺序为：PL细胞、SYGTOREQ、MDCK细胞、JTC-12细胞。用该方法检测细胞类型的敏感顺序为：PL细胞&GT；JTC-12细胞&GT；MDCK细胞。在JTC-12细胞中，碱性磷酸酶(ALPase)、(Na~++K~+)-ATPase和(H~++K~+)-ATPase活性受甲醛浓度依赖性抑制。在MDCK细胞中，碱性磷酸酶(ALPase)和(Na~++K~+)-ATPase活性也被甲醛浓度依赖性地抑制，而(H~++K~+)-ATPase活性被1 mM的甲醛增强，但在高于1 mM的浓度下被抑制。甲醛可增加MDCK细胞的脂质过氧化反应和超氧阴离子自由基的产生。在JTC-12细胞中，甲醛对上述生化指标没有影响。另一方面，甲醛降低了PL细胞中超氧阴离子自由基的产生。这些结果表明，甲醛的这些影响是不同的，取决于细胞的类型和处理的时间。此外，在JTC-12和MDCK细胞中，甲醛以浓度依赖的方式增加细胞内钙离子。此作用可被钙通道阻滞剂维拉帕米抑制，被INT受体阻滞剂TMB-8轻微抑制

The purpose of the present research is to elucidate the biochemical mechanisms of action formaldehyde, the main component of formocresol which is one of root canal disinfectants, using various biochemical parameters in JTC-12, MDCK(from kidney) and PL(from periodontal ligament)cells. Formaldehyde caused leakage of lactate dehydrogenase, and inhibited the uptake of neutral red and the reduction of MTT in a concentration-and time -dependent manner. The testing method as an index of the uptake of neutral red was sensitive in the following order : PL cells(〕SY.gtoreq.〔) MDCK cells > JTC-12 cells. The sensitive sequence of the type of cells by the testing method as an index of the reduction of MTT was PL cells>JTC-12 cells>MDCK cells. In JTC-12 cells, alkaline phosphatase(ALPase), (Na^++K^+)-ATPase and (H^++K^+)-ATPase activities were concentration -dependently inhibited by formaldehyde. In MDCK cells, alkaline phosphatase(ALPase)and(NA^++K^+)-ATPase activities were also concentration-dependently inhibited by formaldehyde, whereas(H^++K^+)-ATPase activity was potentiated by 1mM formaldehyde but inhibited in higher concentrations than 1mM.Formaldehyde had no stimulating effects on leakage of gamma -glutamyl transpeptidase within the range of concentrations examined in both cell. Lipid peroxidation and production of superoxide anion radical were increased by formaldehyde in MDCK cells. In JTC-12 cells, formaldehyde had no effects on these biochemical parameters. On the other hand, formaldehyde lowered the production of superoxide anion radical in PL cells. These results indicated that these effects of formaldehyde was varied, depending on the type of cells and duration of treatment. Furthermore, intracellular calcium ion was increased by formaldehyde in a concentration-dependent manner in JTC-12 and MDCK cells. This effect was inhibited by verapamil, a calcium channel blocker and slightly did by TMB-8, a blocker intr