The growth hormone secretagogue hexarelin improves cardiac function in rats after experimental myocardial infarction

Several studies have shown that GH can enhance cardiac performance in rats after experimental myocardial infarction and in humans with congestive hear t failure. In the present study, the hemodynamic effects of hexarelin (Hex) , an analog of GH-releasing peptide-6 and a potent GH secretagogue, were co mpared with the effects of GH. Four weeks after ligation of the left corona ry artery male rats were treated sc twice daily with hexarelin [10 mu g/kg . day (Hex10) or 100 mu g/kg day (Hex100)], recombinant human GH (2.5 mg/kg day), or 0.9% NaCl for 2 weeks. Transthoracic echocardiography was perform ed before and after the treatment period. GH, but not Hex, increased body w eight gain. GH and Hex100 decreased total peripheral resistance (P < 0.05) and increased stroke volume (P < 0.05 and P < 0.01, respectively) and strok e volume index (P = 0.06 and P < 0.01, respectively) vs. NaCl. Cardiac outp ut was increased by GH and Hex100 (P < 0.05), and cardiac index was increas ed by Hex100 with a borderline significance for GH (P = 0.06). In conclusio n, Hex improves cardiac function and decreases peripheral resistance to a s imilar extent as exogenous GH in rats postmyocardial infarction. The mechan isms of these effects are unclear; they could be mediated by GH or a direct effect of Hex on the cardiovascular system.