Tolerance of the Normotensive and Hypertensive Heart to Global Ischemia and Subsequent Reperfusion

Abstract

PURPOSE: The purpose of this study was to examine the functional responses to global ischemia and subsequent reperfusion in young spontaneously hypertensive (SHR) and normotensive rats (WKY). METHODS: Hearts from female, WKY and SHR (age:8–9 wks; N=6) were isolated and heart performance was measured with a retrogradely perfused, Langendorff, isovolumic preparation (16 ml/min, 5 Hz, 2 mM Ca2+, LVEDP set at 10 mmHg, 95% 02, 5% C02). Hearts were made globally ischemic for 22 minutes and were then reperfused for 10 minutes. RESULTS: Absolute HW and HW/BW ratios were similar between groups. During baseline conditions, perfusion pressures and LV developed pressures (LVDevP) were also similar between groups. There were no differences observed in the time of onset of contracture or in peak contracture during ischemia (WKY; 16.94 ± 0.74 min, SHR; 15.2 ± 0.63 min, P >0.05). Perfusion pressures tended to be greater in SHR at ten minutes of reperfusion (WKY; 112.3 ± 19.2 mmHg, SHR; 159 ± 10.4 mmHg, P = 0.1). Although LV end diastolic pressure (LVEDP) was comparable between groups at ten minutes of reperfusion, both absolute and relative LVDevP were significantly lower in SHR (WKY; 12.1 ± 2.3 mmHg, SHR; 3.5 ± 1.4 mmHg, P < 0.05; WKY; 0.09 ± .01, SHR; 0.03 ± 0.01, p < 0.01). CONCLUSIONS: These data suggest that hearts of young SHR respond comparably to age matched WKY during ischemia, but demonstrate an impaired tolerance to subsequent reperfusion.