Stimulation of myocardial function after brief regional ischemia by glucagon

Glucagon (1.5 to 45 μg/kg, i.v.) has been examined in open‐chest anesthetized dogs subjected to 15 minutes of occlusion of the left circumflex coronary artery (LCCA) and reperfusion. Regional segment lengths in myocardium supplied by the LCCA and left anterior descending (LAD) coronary arteries were measured by sonomicrometry. Occlusion of the LCCA produced paradoxical bulging. At 2.5 hours after reperfusion, segmental shortening in the LCCA area remained significantly reduced at 33 ± 11% of baseline. Regional shortening in the LAD area increased upon LCCA occlusion but was not significantly different from baseline at 2.5 hours. Glucagon increased heart rate and peak positive dP/dt while decreasing systemic pressure. After glucagon 15 μg/kg i. v., LCCA regional shortening was 71 ± 10% of baseline, a significant increase compared with the 2.5 hours reperfusion value. For comparison, isoproterenol 0.3 mg/kg increased segment shortening to 119 ± 19% of baseline. Glucagon reduced end‐diastolic segment length in both LCCA and LAD regions. In conclusion, glucagon significantly improved regional function in myocardium recovering from an episode of regional ischemia.