Heat shock response in the liver: expression and regulation of the hsp70 gene family and early response genes after in vivo hyperthermia.

Heat shock response in cultured cells has been studied extensively; however few data are available on heat shock response in an intact organ of a living animal. In this study we analyzed the kinetics of expression of the heat shock protein 70 gene family (heat shock protein 70, heat shock cognate protein 73 and glucose-regulated protein 78) in the liver of the thermally stressed rat. New synthesis of heat shock protein 70 and heat shock cognate protein 73 was shown in liver slices pulse labeled in vitro with 35S-methionine. Accumulation of heat shock protein 70 and heat shock cognate protein 73 proteins was shown in total cellular extracts. 32P-labeled complementary DNA probes encoding heat shock protein 70, heat shock cognate protein 73 and glucose-regulated protein 78 were used to show that the levels of the corresponding messenger RNAs increase as a fraction of total RNA and in polysomes at different extents and with different kinetics. The induction of heat shock protein 70 and heat shock cognate protein 73 messenger RNAs reflected the increase in the synthesis of the corresponding proteins. Run-on transcription analysis indicated that the expression of heat shock protein 70 and heat shock cognate protein 73 genes was mainly regulated at the transcriptional level. On the contrary, both transcriptional and posttranscriptional regulatory mechanisms can explain the induction of the glucose-regulated protein 78 gene.(ABSTRACT TRUNCATED AT 250 WORDS)