Coronary reserve in spontaneously hypertensive rats: the effect of blood pressure, hypertrophy and longterm vasodilator therapy
Coronary reserve in man is reduced in concentric hypertensive hypertrophy. In 65-week-old spontaneously hypertensive rats (SHR) we found similar changes; in perfusion studies on isolated hearts the vasodilating capacity was restricted in comparison to Wistar Kyoto rats (WKY). Minimal coronary vascular resistance was 0.12 mm Hg · min · 100 g/ml versus 0.05 units in WKY (p < 0.0001). 60 weeks of antihy-pertensive therapy with hydralazine reduced coronary vascular resistance to 0.07 units (p< 0.0001). Under this treatment, blood pressure and heart weight/body weight ratios were also significantly reduced. Metoprolol, even when applied in high doses, reduced coronary vascular resistance only to 0.09 units (p< 0.0001); despite a modest reduction in blood pressure, the degree of myocardial hypertrophy remained constant. It may be concluded that an increase in coronary vascular resistance in SHR can be prevented by antihypertensive treatment with hydralazine; metoprolol treatment is less effective.
Key wordscoronary reserve coronary resistance SHR — long-term antihypertensive therapy hydralazine metoprolol essential hypertension cardiac hypertrophy
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