TY - JOUR
T1 - Beating myocardium counteracts myogenic tone of coronary microvessels
T2 - Involvement of ATP-sensitive potassium channels
AU - Takeda, Satoru
AU - Komaru, Tatsuya
AU - Takahashi, Katsuaki
AU - Sato, Kouichi
AU - Kanatsuka, Hiroshi
AU - Kokusho, Yasunori
AU - Shirato, Kunio
AU - Shimokawa, Hiroaki
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2006
Y1 - 2006
N2 - 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 < 0.05 vs. without contact), and myogenic tone was reduced by ∼40%. When endothelium of DV was denuded, the shift persisted, but the degree of shift was reduced to 10% (P < 0.05 vs. with endothelium). The shift was abolished by glibenclamide, an ATP-sensitive potassium (KATP) channel blocker. A similar upward shift was induced by rapid pacing, but the shift was not blocked by glibenclamide. We conclude that the beating myocardium counteracts myogenic tone by releasing transferable vasoactive signals that affect the endothelium and the vascular smooth muscle, and that the signals are solely mediated by the activation of KATP channels, unlike the rapid pacing-induced vasoactive factors.
AB - 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 < 0.05 vs. without contact), and myogenic tone was reduced by ∼40%. When endothelium of DV was denuded, the shift persisted, but the degree of shift was reduced to 10% (P < 0.05 vs. with endothelium). The shift was abolished by glibenclamide, an ATP-sensitive potassium (KATP) channel blocker. A similar upward shift was induced by rapid pacing, but the shift was not blocked by glibenclamide. We conclude that the beating myocardium counteracts myogenic tone by releasing transferable vasoactive signals that affect the endothelium and the vascular smooth muscle, and that the signals are solely mediated by the activation of KATP channels, unlike the rapid pacing-induced vasoactive factors.
KW - Coronary microcirculation
KW - Endothelium
KW - Myocardial metabolism
KW - Vasodilation
KW - Vasomotor signals
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U2 - 10.1152/ajpheart.00039.2006
DO - 10.1152/ajpheart.00039.2006
M3 - Article
C2 - 16861700
AN - SCOPUS:33845416890
VL - 291
SP - H3050-H3057
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6135
IS - 6
ER -