[Biologic effects of hyperthermia and radiation on gastric cancer cells (SGC-7901) in vitro--I. Influence on cell growth curve, number of colonies and mitosis].

Biologic effects of hyperthermia (42 degrees-44 degrees C) and radiation on SGC-7901 were studied quantitatively and morphologically. Action of hyperthermia and radiation on the population and subpopulation of cells was monitored by cell growth curve and colony counts. The results show that both hyperthermia (43 degrees C for 30 min) and radiation (500 rad) can cause the cell kill and growth curve decrease but the cells still tend to proliferate. The synergistic action of heat plus radiation is demonstrated when they are given in the interval of 30 min. The thermal enhance rate was 1.27 and 1.37 for survival rate down to 2% and 5%. The concentration of potassium ions in the media is increased with cell kill after heat and radiation. The damage from heating appears like a direct kill or immediate death, the damage from radiation reveals delayed or metabolic death. Partial and transitory redistribution of cell cycle occurs following heating or radiation. Delayed division is more marked following heating than radiation. The synchronization effect may be used to hit the cycling tumor cells in the most radiosensitive phase.