Effects of early treatment with growth hormone on infarct size, survival, and cardiac gene expression after acute myocardial infarction.

Objective: This study examined the effects of growth hormone (GH) on infarct size, survival, and cardiac gene expression in rats with acute myocardial infarction.

Design: Animals randomly received sc injection of either saline vehicle (n = 98) or GH (2mg/kg/day, n = 105) for 14 days commencing the day of left coronary artery ligation. Infarct size was determined by morphometric analysis at the time of death or at 52 weeks post-surgery. Gene expression was analyzed by real-time RT-PCR after 2-week treatment.

Results: GH decreased infarct size by 18% (P < 0.01) and increased survival by 36% at 52 weeks. GH also significantly reduced cardiac expression of atrial natriuretic factor, beta-myosin heavy chain, alpha-smooth muscle actin, collagen I, collagen III, fibronectin, and pro-inflammatory cytokines.

Conclusions: Treatment with GH for 2 weeks beginning on the day of myocardial infarction produced beneficial effects that were associated with reductions in cardiac gene expression symptomatic of pathological remodeling.