Growth hormone improves bioenergetics and decreases catecholamines in postinfarct rat hearts

The aims of this study were to examine, in vivo, the effects of GH treatmen t on myocardial energy metabolism, function, morphology, and neurohormonal status in rats during the early postinfarct remodeling phase. Myocardial infarction (MI) was induced in male Sprague Dawley rats. Three d ifferent groups were studied: MI rats treated with saline (n = 7), MI rats treated with GH (MI + GH; n = 11; 3 mg/kg.day), and sham-operated rats (sha m; n = 8). All rats were investigated with P-31 magnetic resonance spectros copy and echocardiography at 3 days after MI and 3 weeks later. After 3 wee ks treatment with GH, the phosphocreatine/ATP ratio increased significantly , compared with the control group (MI = 1.69 +/- 0.09 vs. MI + GH = 2.42 +/ - 0.05, P < 0.001; sham = 2.34 +/- 0.08). Treatment with GH significantly a ttenuated an increase in left ventricular end systolic volume and end diast olic volume. A decrease in ejection fraction was prevented in GH-treated ra ts (P < 0.05 vs, MI). Myocardial and plasma noradrenaline levels were signi ficantly lower in Nn: rats treated with GH. These effects were accompanied by normalization of plasma brain natriuretic peptide levels (sham = 124.1 /- 8.4; MI = 203.9 +/- 34.7; MI + GH = 118.3 +/- 8.4 ng/ml; P < 0.05 vs. MI ). In conclusion, GH improves myocardial energy reserve, preserves left ventri cular function, and attenuates pathologic postinfarct remodeling in the abs ence of induction of left ventricular hypertrophy in postinfarct rats. The marked decrease in myocardial content of noradrenaline, after GH treatment, may protect myocardium from adverse effects of catecholamines during posti nfarct remodeling.