Cytoskeletal thermotolerance in NRK cells

Abstract

We investigated the effect of heat shock on the cytoskeletons (actin stress fibres, intermediate filaments and microtubules) and the relation between thermotolerance of cytoskeletons and thermotolerance as defined by clonogenic survival in normal rat kidney (NRK) cells. Upon heating at 45 degrees C for 15 min, almost all actin stress fibres were disrupted. During the recovery period after heat shock the stress fibres were reorganized rapidly and returned to their preheated state by 16 h. When the cells were heated again at 45 degrees C for 15 min, the disruption of stress fibres was less severe, indicating thermotolerant state of stress fibres. However, the thermotolerant state of stress fibres induced by prior treatment with sodium arsenite or by heating at 42 degrees C for 2 h was less evident than that induced by prior heat shock at 45 degrees C. The intermediate filaments in NRK cells were very heat-resistant; no apparent changes were observed even after heat shock at 45 degrees C for 60 min, and prior conditioning treatments could not induce thermotolerance of microtubules. All prior conditioning treatments could induce heat shock proteins and thermotolerance as defined by clonogenic survival. From these results it is suggested that there is no correlation between cytoskeletal thermotolerance and either heat shock protein level or thermotolerance as defined by clonogenic survival in NRK cells.