Mepindolol is a newly developed
beta-adrenergic blocking agent reported to counteract the chronotropic effect of
catecholamines, with only little effect on contractility. This study was designed to assess whether or not
mepindolol is effective in reducing
infarct size. Accordingly, 16 rats, serving as controls, underwent coronary artery occlusion and did not receive any treatment; an additional 19 were treated with
mepindolol (1 mg/kg s.c. t.i.d.) for 48 h. Finally, a third group (n = 18) underwent
sham operation. Forty-eight hours later,
infarct size was calculated from left ventricular
creatine phosphokinase activity and found to average 52.4 +/- 7.8% (mean +/- SEM) of the left ventricle in control rats and 35.6 +/- 5.4% in treated rats (p less than 0.05). Left ventricular
phospholipid content averaged 0.79 +/- 0.08 microgram P/mg
protein in
sham-operated rats and 0.61 +/- 0.04 microgram P/mg
protein in control animals. In contrast, in
mepindolol-treated rats,
phospholipid concentration was 0.70 +/- 0.04 microgram P/mg
protein (p less than 0.05), this suggesting a protective effect of the
drug on
ischemia-induced
phospholipid degradation. The long-term effect of
mepindolol on left ventricular
hydroxyproline concentration was assessed 21 days post-
coronary occlusion.
Infarct size calculated by this method was 30.2 +/- 4.8% of left ventricle in 21 control animals and 18.2 +/- 4.2% in 28 treated rats (p less than 0.05), indicating that, as for the acute
necrosis, the extent of
scar development after coronary artery occlusion can be reduced by
mepindolol.