[The relationship between thermotolerance and the tissue oxygen tension in human gastric cancer tissue]

To study the relationship between thermotolerance and post-thermal phenomenon, tumor pO2 (TpO2) in xenoplanted gastric cancer tissue (H-23) has been measured by a polarographic method. The heat treatment was done in a water bath at 43.5 +/- 0.1 degrees C for 23 minutes. In order to produce thermotolerance, the second treatment was carried out at an interval of 24 hours, or, alternatively at 72 hours, or at 5 days or at 7 days. The thermotolerance of the H-23 tumor reached its maximum at the 72 hour-interval and was seen to disappear completely at 7 days. The TpO2 in the H-23 tumor decreased immediately after a single heat treatment and returned to its pre-treated value after 10 hours. In cases of the second heat treatment, the 72-hour interval group returned to its pre-treated value in 2-6 hours, whereas the 24-hour, 5-day, and 7-day interval groups showed a longer recovery time. The relationship between thermotolerance and TpO2 recovery was inverse at r = -0.858 and p = 0.035. Thus, our study suggests that not only is the thermotolerance affected by the alteration of the intra-cellular components, but also by the post-thermal changes in the tumor vessels.