| Co-Investigator(Kenkyū-buntansha) |
SHIMURA Mari Nihon University, Dental Research Center, Assistant Profesor., 歯学部, 助手 (90226267)
MAJIMA Hideyuki Fukui Medical University, Department of Experimental Radiology and Health Physic, 医学部, 助教授 (60165701)
WAKAMATSU Yoshiko Nihon University, Department of Pharmacology, Associate Profesor., 歯学部, 助教授 (30059084)
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| Research Abstract |
Effects of micro environmental factors, i. e., hypoxic, low-pH, low-nutrient, as well as thermotolerance on cytotoxicity of thermo-chemo therapy were studied in virto. To examine effects of thermochemotherapy, all treatments were given by immersing culture flasks into a water bath where a givenn temperature (〕SY.+-.〔) 0.05 ﾟC was maintained by a heater circulator. Following 10 to 14 days incubation, colonies were stained and counted, and surviving fraction was calculated. Preheated cells were treated with cis-DDP or BLM at 37 or 43 ﾟC various times after heating. The results indicaded that the interaction between BLM treatment and the kinetics of thermotolerance was similar to that for cis-DDP.However, the enchancement of BLM cytotoxicity by preheating was much less extensive compared to that of cis-DDP cytotoxicity. Preheating decreased the magnitude of thermal sensitization of drug cytotoxicity. The magnitude of this decrease appeared to be parallel to the kinetics of themotolerance. This study also demonstrates that pretreatment CHO cells by cis-DDP or BLM dose not alter the sensitivity to subsequent drug treatment, hyperthermia or thermochemotherapy. Low-pH micro-environmental condition was also focused and a change in pH effect was studied, comparing to change in intracellular pH in CHO cells that had been cultured for various periods at low pH.Chronic low pH (pH 6.8) cultures were established by incubating under 27% CO_2 and 73% air in a humidified incbator at 37 ﾟC for 0 to 10 weeks. The cells were heated in this medium at 43 (〕SY.+-.〔) 0.05 ﾟC, followed to colony formation. Intracellular pH (pHi) was measured using the pH-sensitive fluorescent dye BCEF / AM (Dojingo, Japan) originally employed by Thomas et al.. The pH effect was observed by obtaining cell survival cueves at both pH 7.2 and 6.8 at 43 ﾟC, and then comparing them. The differences between the surviving fractions at both pH values became almost the same by three days of culture, and by 5
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