Activation of heat-shock transcription factor in rat heart after heat shock and exercise.

Stress-induced transcriptional regulation of the heat-shock proteins (HSP) is mediated by activation and binding of the heat-shock transcription factors (HSF) to the heat-shock element (HSE). Given the similarities between the stressors known to activate the HSF in cultured cells and the physiological stresses known to occur during exercise, HSF activation was examined in the hearts from exercising animals. Sprague-Dawley rats (5 rats/group) were run on a treadmill (24 m/min) for either 0, 20, 40, or 60 min or to exhaustion (102 +/- 7 min). Protein extracts were assessed for HSF activation by mobility-shift gels. Extracts from the hearts of nonrunning rats demonstrated no HSF activation, whereas HSF activation was detected in 80% of the hearts from animals that run for at least 40 min. These results demonstrate that treadmill running is capable of activating the HSF and increasing 70-kDa HSP mRNA in the rat myocardium.