Beating myocardium counteracts myogenic tone of coronary microvessels: involvement of ATP-sensitive potassium channelsSatoru Takeda, Tatsuya Komaru, Katsuaki Takahashi, Kouichi Sato, Hiroshi Kanatsuka, Yasunori Kokusho, Kunio Shirato, and Hiroaki Shimokawa
Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
Myogenic tone is intrinsic to vascular tissue and plays an important role in determining basal coronary resistance. However, the effect of the beating heart on myogenic tone is unknown. We investigated the effects of myocardium-derived vasoactive factors on the myogenic tone of coronary microvessels in the resting condition and during increased metabolism. Pressurized isolated coronary vessels (detector vessel, DV) of rabbits (n = 33, maximal inner diameter 201 ± 8 µm) were gently placed on beating hearts of anesthetized dogs and observed with an intravital microscope equipped with a floating objective. To shut off the myocardium-derived vasoactive signals, we placed plastic film between DV and the heart. The intravascular pressure was changed from 120 to 60 cmH2O, and pressure-diameter curves were obtained with and without the contact of DV and the myocardium. The direct contact shifted the pressure-diameter curve upward (P <>
coronary microcirculation; vasomotor signals; vasodilation; myocardial metabolism; endothelium
Am J Physiol Heart Circ Physiol 291: H3050-H3057, 2006.
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