Insulin improves functional and metabolic recovery of reperfused working rat heart.
BACKGROUND
Glucose, insulin, and potassium solution improves left ventricular function in refractory pump failure. Direct effects of insulin on the heart cannot be determined in vivo. We hypothesized that insulin has a direct positive inotropic effect on the reperfused heart.


METHODS
Isolated working rat hearts were perfused with buffer containing glucose (5 mmol/L) plus oleate (1.2 mmol/L). Hearts were subjected to 15 minutes of ischemia and reperfused with or without insulin (100 microU/mL) for 40 minutes. Epinephrine (1 micromol/L) was added for the last 20 minutes.


RESULTS
Hearts recovered 51.1% of preischemic cardiac power in the absence and 76.4% in the presence of insulin (p < 0.05). Whereas oleate oxidation remained unchanged, glucose uptake and oxidation increased during reperfusion with epinephrine (p < 0.01). This increase was significantly greater when hearts were reperfused in the presence of insulin (p < 0.01). Insulin also prevented an epinephrine-induced glycogen breakdown during reperfusion (p < 0.05).


CONCLUSIONS
Insulin has a direct positive inotropic effect on postischemic rat heart. This effect is additive to epinephrine and occurs without delay. Increased rates of glucose oxidation and net glycogen synthesis are more protracted.
Doenst
T
T
Department of Medicine, The University of Texas-Houston Medical School, 77030, USA.
Richwine
R T
RT
Bray
M S
MS
Goodwin
G W
GW
Frazier
O H
OH
Taegtmeyer
H
H
D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D005947:Glucose / Q000378:metabolism; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002316:Cardiotonic Agents; D007328:Insulin; D005947:Glucose