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Objective: To assess the effect of growth hormone (GH) on myocardial remodeling in infarcted rats., Methods: This study comprised 24 Wistar rats divided into 3 groups as follows: 1) AMI-GH group--comprising 8 rats that underwent infarction and were treated with GH; 2) AMI group--comprising 8 rats that underwent infarction and received only the diluent of the GH solution; and 3) control group (C group)--comprising 8 rats that underwent simulated infarction. After 30 days, the animals underwent functional study through echocardiography, and the changes in myocardial contractility of the isolated left ventricular (LV) papillary muscle were studied., Results: The echocardiography identified an increase in the diastolic (C=7.32+/-0.49; AMI=8.50+/-0.73; AMI-GH=9.34+/-0.73; P<0.05) and systolic (C=3.38+/-0.47, AMI=5.16+/-1.24; AMI-GH=5.96+/-1.54; P<0.05) diameters (mm) in the LV of the infarcted animals. The AMI-GH group animals had a lower ejection fraction (%) (C=0.9+/-0.03; AMI=0.76+/-0.12; AMI-GH= 0.72+/- 0.14; P<0.05 for C vs AMI-GH) compared with those in controls. The study of the isolated left ventricular papillary muscle showed that the AMI-GH group had changes (C=1.50+/-0.59; AMI=1.28+/-0.38; AMI-GH=1.98+/-0.41; P<0.05 for C vs AMI-GH) only in the tension at rest (TR - g/mm2) and in the time delta for a 50% decrease in the tension developed (TR50, ms) after stimulation with calcium (C=23.75+/-9.16; AMI=-16.56+/-14.82; AMI-GH=-4.69+/-8.39; P<0.05 for C vs AMI-GH) and in the delta of tension developed (TD, g/mm2) after stimulation with isoproterenol (C=0.99+/-0.17; AMI=0.54+/-0.62; AMI-GH=0.08+/-0.75; P<0.05 for C vs AMI-GH) compared with those in control animals., Conclusion: The early administration of GH in the experimental infarction model in rats may result in adverse effects on the process of ventricular remodeling.