Heat shock protein expression in hearts hypertrophied by genetic and nongenetic hypertension

Genetically hypertensive animals are characterized by greater thermosensiti vity and overexpression of heat shock proteins (HSP) upon thermal stimulati on. We examined HSP72 expression under conditions of brief coronary occlusi on or thermal stimulation,, and the effects of the severity of these stimul i and of myocardial hypertrophy on the expression in hearts of spontaneousl y hypertensive rat (SHR) and Wistar Kyoto rat (WKY) groups, A snare was cre ated around the left coronary artery in the SHR (n = 16) and WKY (n = 19) g roups. In 7 WKY rats, the ascending aorta was banded and a snare was create d simultaneously (WKY-AoB). By tying the snare, 4 weeks later, we applied 5 - or 10-min coronary occlusion without opening the chest. For thermal stimu lation, the SHR (n = 13) and WKY (n = 11) rats were placed in a 42 degrees C chamber for 15 or 40 min. The mRNA or protein level was estimated 1 or 24 h after stimulation. In the SHR vs WKY groups, the mRNA and protein levels were higher after 5-min occlusion or 15-min thermal stimulation. After 10-m in occlusion or 40-min thermal stimulation the difference was no longer obs erved. The overexpression was not observed in the WKY-AoB group despite the presence of hypertrophy similar to that seen in the SHR group (3.11 +/- 0. 11 vs 3.20 +/- 0.06mg/g in left ventricular weight/body weight). The HSP72 was overexpressed in hearts of genetically hypertensive animals after brief ischemia. Differential expression between the two groups was observed afte r mild stimuli, but not after more severe stimuli. Cardiac hypertrophy was not a major factor for determining the overexpression of HSP72.