Losartan attenuates myocardial ischemia-induced ventricular arrythmias and reperfusion injury in spontaneously hypertensive rats.
To assess the efficacy of losartan (2-n-butyl-4-chloro-5-hydroxymethyl-1-[(2'-(1H-tetrazol-5-yl)biphe nyl-4-yl)methyl]imidazole, potassium salt), an angiotensin II receptor antagonist, on acute myocardial ischemia, 36 four-month-old spontaneously hypertensive rats were used. The animals underwent 45 min of left coronary artery occlusion and 1 h of reperfusion and were randomly assigned to control and losartan-treated groups (2, 5, and 10 mg/kg, intravenously). Losartan was administered 15 min before ischemia. Electrocardiograms (lead II) were monitored continuously throughout the experiment. To assess the anti-infarct effect of losartan, the area at risk was determined by methylene blue dye and the infarct size was determined by nitroblue tetrazolium chloride staining. The areas of risk and infarct were measured by computerized planimetry. Results demonstrated that the low and intermediate doses (2 and 5 mg/kg) of losartan significantly decreased the incidence of ventricular fibrillation and mortality during the ischemic period induced by left coronary artery occlusion. However, a significant reduction in infarct size, calculated as a percentage of the area at risk, was noted in all three losartan-treated groups (control: 41.5% +/- 5.2%, losartan, 2 mg/kg: 11.2% +/- 5.8%, 5 mg/kg: 8.5% +/- 2.7% and 10 mg/kg: 13.7% +/- 1.6%). The results suggest that losartan may be useful in the treatment of ventricular arrhythmias induced by acute myocardial infarction and attenuation of reperfusion injury in hypertension.
Lee
Y M
YM
Department of Pharmacology, Tri-Service General Hospital, Taipei, Taiwan.
Peng
Y Y
YY
Ding
Y A
YA
Yen
M H
MH
D000208:Acute Disease; D000804:Angiotensin II / Q000378:metabolism*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D001145:Arrhythmias, Cardiac / Q000188:drug therapy* / Q000209:etiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006439:Hemodynamics / Q000187:drug effects; D019808:Losartan / Q000627:therapeutic use*; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology / Q000503:physiopathology; D017202:Myocardial Ischemia / Q000150:complications*; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy*; D051381:Rats; D011918:Rats, Inbred SHR
D057911:Angiotensin Receptor Antagonists; D000889:Anti-Arrhythmia Agents; D000804:Angiotensin II; D019808:Losartan