Induction of thermotolerance and heat-shock protein synthesis during nutritional deprivation

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Abstract
Under various conditions of heating, H35 cells were submitted to acute nutritional deprivation by omitting a number of substrates (L15D medium). At 37°C cell death starts after a lag-period of 3–5 h. During hypothermia cell death is delayed, whereas during hyperthermia it is accelerated especially as a result of thermosensitization. In L15D the ATP level decreases approximately 3 times faster in combination with hyperthermia than at 37°C. In non-thermotolerant cells thermosensization is very high at 41°C and decreases with increasing temperature; in thermotolerant cells it is comparatively decreased at 41°C and increased at 42·5°C and above. In response to a heat shock of 30 min at 42·5°C only 10% of the cell population expresses acute thermotolerance after incubation at 37°C in L15D as compared to nearly 100% in complete medium (L15C). Chronic development of thermotolerance appears to be even more repressed in the presence of L15D, which partly explains the high thermosensitization at 41 °C. Changes in the rate of protein synthesis for combinations of nutritional deprivation and hyperthermia show a correlation with the cell survival data. Development of acute thermotolerance in L15D is accompanied by an increase in heat-shock protein synthesis relative to total protein. At 41°C in L15D no heat-shock protein induction could be detected. Of the omitted substrates only glutamine can effectively abolish thermosensitization and the effects of L15D on protein and heat-shock protein synthesis depending on the condition of the cells, thermotolerant or non-thermotolerant, and to a different extent for the various proteins considered.