title: Mechanisms of antifibrillatory effect of acidic reperfusion: role of perfusate bicarbonate concentration.
abstract: Transient (2 min) acidic (pH 6.6) reperfusion with low [HCO3-] solution suppresses reperfusion-induced ventricular fibrillation (VF) in the isolated rat heart. Using this preparation, we tested whether the effect was mediated by the high [H+] or the low [HCO3-] of perfusate. Left and right coronary beds were independently perfused with HCO3(-)-containing (25.0 mmol/l) solution at pH 7.4. Regional ischemia was then induced by stopping flow to the left coronary bed for 10 min. Hearts were subsequently assigned to four groups (n = 12 hearts/group), and the left coronary bed was reperfused with either HCO3(-)-containing (25.0 or 4.0 mmol/l) or HCO3(-)-free (5.0 mmol/l HEPES) solution, at pH 7.4 throughout (control reperfusion) or at pH 6.6 for the first 2 min and at pH 7.4 from 2 to 5 min (acidic reperfusion). Regardless of the buffer, controls exhibited a high (92 and 100%) incidence of VF; this was reduced to 42% in both of the acidic reperfusion groups (P < 0.05). There were no intergroup differences in heart rate, coronary flow, or size of ischemic zone. Thus high [H+], rather than low [HCO3-], appears to mediate the antifibrillatory effect of transient acidic reperfusion.
authors.affiliation: Rayne Institute, St. Thomas' Hospital, London, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Ibuki
authors.forename: D J
authors.initials: DJ
authors.lastname: Hearse
authors.forename: M
authors.initials: M
authors.lastname: Avkiran
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000517:prevention & control*; D001639:Bicarbonates / Q000008:administration & dosage*; D002021:Buffers; D003326:Coronary Circulation; D006339:Heart Rate; D006352:Heart Ventricles; D006863:Hydrogen-Ion Concentration; D008297:Male; D017202:Myocardial Ischemia / Q000503:physiopathology; D015425:Myocardial Reperfusion; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D001639:Bicarbonates; D002021:Buffers