Regional myocardial heat-shook protein (HSP70) concentrations under different blood from conditions

The concentration of heat-shock proteins of 70 kD (HSP70) in heart tissue h as been shown to increase during transient myocardial. ischaemia and to per sist during several hours of reperfusion. In this study the relationship be tween the local myocardial HSP70 concentration and blood flow was addressed for control physiological conditions and acute myocardial ischaemia. A spe cific aim of this study was to address the question of whether low flow are as under control physiological conditions have undergone a transient ischae mia during the preceding hours and thus may be in a state of hibernation or stunning. In 12 anaesthetized, open-chest beagle dogs (6 control and 6 wit h 60-min coronary artery stenosis) heart rate, mean aortic pressure, mean a rterial partial pressure of O-2 and partial pressure of CO2 averaged 85+/-1 6 beats/min, 94+/-14 mmHg, 102+/-17 mmHg and 39+/-6 mmHg, respectively. Reg ional HSP70 and myocardial blood flow (RMBF) were measured using an HSP70-e nzyme-linked immunosorbent assay and the tracer microsphere technique, resp ectively, in samples of 250 mg wet mass. In the control group the mean RMBF was 1.06+/-0.59 ml.min(-1).g(-1) and the local HSP70 concentration was 7.0 8+/-1.03 mu g/mg cytosolic protein. Myocardial HSP70 showed a blood flow-in dependent regional biological heterogeneity, equivalent to a coefficient of variation of 0.31. Local HSP70 concentrations did not differ (P>0.05) betw een control low and high flow samples, 6.16+/-1.0 vs 6.08+/-0.75 mu g/mg cy tosolic protein, respectively. However, after 60 min of coronary artery occ lusion the local HSP70 concentration increased from 7.08+/-1.03 to 13.43+/- 3.19 mu g/mg cytosolic protein (P<0.001). There was a significant inverse r elationship between the percent reduction of local blood flow and HSP70 (r= -0.56, P<0.001). From these results it is concluded that: (1) low flow samp les under control physiological conditions are unlikely to be in a state of hibernation or stunning since their HSP70 concentration is normal and (2) the increase in the local HSP70 concentration during myocardial ischaemia r eflects the degree of impairment of O-2 delivery.