Effects of EDRF and alpha-sympathetic activity on coronary slosh phenomenon

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The purpose of this study was to investigate the relation between coronary slosh phenomena and endothelium derived relaxing factor (EDRF). In anesthetized dogs, phasic septal artery blow was measured by 20MHz 80channel ultrasound velocimeter. Subendocardial arteriole was observed by needle-probe videomicroscope in the physiologically beating heart. Subendocardial coronary arteriolar diameter diminished from end-diastole to end-systole by about 20%, indicating that the coronary slosh phenomena is caused by the compression of subendocardial coronary arteriole due to myocardial contraction. Stimulation of alpha sympathetic activity diminishes coronary tonus. In dogs with hypertensive cardiac hypertrophy induced by two kidney two chips, coronary slosh increased. In the same dogs, subendocardial vasodilatory capacity which is dependent on endothelium was jeopardized, whereas endothelium independent capacity was not jeopardized. These results indicate that coronary slosh may be related to both coronary tonus by EDRF and myocardial contraction.