Microvascular sites and mechanisms responsible for reactive hyperemia in the coronary circulation of the beating canine heart

Hiroshi Kanatsuka, Nobuyo Sekiguchi, Kouichi Sato, Kenjiro Akai, Yan Wang, Tatsuya Komaru, Kouichi Ashikawa, Tamotsu Takishima

Research output: Contribution to journalArticlepeer-review

94 Citations (Scopus)

Abstract

Our aim was to elucidate the site and mechanism responsible for reactive hyperemia in coronary circulation. In in vivo beating canine hearts, microvessels of the left anterior descending coronary artery (LAD) were observed through a microscope equipped with a floating objective. Flow velocity of the LAD was measured with a suction-type Doppler probe. The LAD was occluded for 20 or 30 seconds and then released, and reactive hyperemia was observed before and after 8-phenyltheophylline (7.5 mg/kg i.v.) or glibenclamide (200 μg/kg into the LAD) infusion. During the occlusion, only arterial microvessels smaller than 100 μm in diameter dilated. Dilation of those vessels was partially attenuated by 8-phenyltheophylline and completely abolished with glibenclamide. In the early phase of reactive hyperemia, all arterial microvessels dilated, and the magnitude of peak dilation was greater in vessels smaller than 100 μm compared with those larger than 100 μm. Vasodilation during reactive hyperemia ceased within 60 seconds in vessels smaller than 100 μm but was sustained for more than 120 seconds in those larger than 100 μm. 8-Phenyltheophylline did not change peak dilation of arterial microvessels but reduced dilation after the peak. Glibenclamide remarkably attenuated dilation of all arterial microvessels in the whole phase of reactive hyperemia. These results indicate that all arterial microvessels are responsible for reactive hyperemia after coronary artery occlusions of 20-30 seconds, but there is greater participation of vessels smaller than 100 μm in the early phase of reactive hyperemia. Dilation of vessels larger than 100 μm assumes an important role in the later phase. ATP-sensitive K+ channels mediate dilation of arterial microvessels both in brief ischemia and reactive hyperemia.

Original languageEnglish
Pages (from-to)912-922
Number of pages11
JournalCirculation research
Volume71
Issue number4
DOIs
Publication statusPublished - 1992 Oct

Keywords

  • ATP-sensitive K channel
  • Adenosine
  • Coronary microcirculation
  • Floating objective

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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