INSULIN IMPROVES CONTRACTILE FUNCTION DURING MODERATE ISCHEMIA IN CANINE LEFT-VENTRICLE

This study determined the effects of insulin on myocardial contractile function and glucose metabolism during moderate coronary hypoperfusio n. Coronary perfusion pressure (CPP) was lowered from 100 to 60, 50, a nd 40 mmHg in the left anterior descending coronary artery of anesthet ized, open-chest dogs. Regional glucose uptake (GU), lactate uptake, m yocardial O-2 consumption, and percent segment shortening (%SS) mere m easured without (n = 12) or with intravenous (4 U/min, n = 12) or intr acoronary insulin (4 U/min, n = 6). Glucose metabolites were also meas ured in freeze-clamped biopsies of control heart (n = 6) and hearts tr eated with intravenous insulin (n = 6) at the completion of the protoc ol (40 mmHg CPP). GU increased with intravenous and intracoronary insu lin (P < 0.01). In all groups, GU was unaffected by reduced CPP, altho ugh lactate uptake decreased significantly (P < 0.01). Myocardial O-2 consumption fell (P < 0.05) as CPP was lowered in all groups and was n ot altered significantly by intravenous or intracoronary insulin treat ment. without insulin, %SS decreased 72% (P < 0.05) at 40 mmHg CPP, bu t in hearts treated with intravenous and intracoronary insulin, %SS wa s not reduced (P > 0.05). Myocardial glycogen, alanine, lactate, and p yruvate contents were not significantly different in untreated hearts and hearts treated with intravenous insulin. Thus, in moderately ische mic canine myocardium, insulin markedly improved regional contractile function and did not appreciably increase the products of anaerobic gl ucose metabolism.