Role of pertussis toxin-sensitive G protein in metabolic vasodilation of coronary microcirculation

Toshinori Tanikawa, Hiroshi Kanatsuka, Ryohji Koshida, Mitsuaki Tanaka, Akihiko Sugimura, Toshinobu Kumagai, Masahito Miura, Tatsuya Komaru, Kunio Shirato

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

We have previously demonstrated that pertussis toxin (PTX)-sensitive G protein (G(PTX)) plays a major role in coronary microvascular vasomotion during hypoperfusion. We aimed to elucidate the role of G(PTx) during increasing metabolic demand. In 18 mongrel dogs, coronary arteriolar diameters were measured by fluorescence microangiography using a floating objective. Myocardial oxygen consumption (MVO2) was increased by rapid left atrial pacing. In six dogs, PTX (300 ng/ml) was superfused onto the heart surface for 2 h to locally block G(PTX). In eight dogs, the vehicle (Krebs solution) was superfused in the same way. Before and after each treatment, the diameters were measured during control (130 beats/min) and rapid pacing (260 beats/min) in each group. Metabolic stimulation before and after the vehicle treatment caused 8.6 ± 1.8 and 16.1 ± 3.6% dilation of coronary arterioles <100 μm in diameter (57 ± 8 μm at control, n = 10), respectively. PTX treatment clearly abolished the dilation of arterioles (12.8 ± 2.5% before and 0.9 ± 1.6% after the treatment, P < 0.001 vs. vehicle; 66 ± 8 μm at control, n = 11) in response to metabolic stimulation. The increases in MVO2 and coronary flow velocity were comparable between the vehicle and PTX groups. In four dogs, 8-phenyltheophylline (10 μM, superfusion for 30 min) did not affect the metabolic dilation of arterioles (15.3 ± 2.0% before and 16.4 ± 3.8% after treatment; 84.3 ± 11.0 μm at control, n = 8). Thus we conclude that G(PTX) plays a major role in regulating the coronary microvascular tone during active hyperemia, and adenosine does not contribute to metabolic vasodilation via G(PTX) activation.

Original languageEnglish
Pages (from-to)H1819-H1829
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume279
Issue number4 48-4
DOIs
Publication statusPublished - 2000

Keywords

  • Active hyperemia
  • Coronary circulation
  • Guanine nucleotide regulatory protein

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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