Prior treatment with heat shock attenuates the stress response in isolated working rat hearts

We examined the expression of the mRNAs encoding for the inducible heat shock protein (HSP) 71 and the constitutively synthesized HSP73 in control and 24-h post-heat-shocked (post-HS) hearts during isolated working heart perfusion. Paired control and 24-h post-HS rat hearts were perfused in the working heart mode for 1, 2, 3, or 4 h. Aortic and coronary flow rates and heart rates were not different between the control and 24-h post-HS hearts during the perfusion periods. After perfusion, total RNA was extracted and separated by gel electrophoresis. RNA was blotted to membranes, subsequently probed with 32P-labelled cDNA probes for HSP71 and HSP73 transcripts, and autoradiographed. Control hearts showed a sharp increase in transcripts for HSP71 and a more moderate increase in transcripts for HSP73 accumulation during perfusion. However, the increase in HSP71 and HSP73 transcripts in the HS hearts was markedly less than that in the control hearts. This suppression in gene expression in the HS hearts seems to suggest a negative control mechanism regulating transcription of mRNA encoding HSP71 and HSP73.