Hemodynamic and hormonal effects of human ghrelin in healthy volunteers

To investigate hemodynamic and hormonal effects of ghrelin, a novel growth hormone (GH)-releasing peptide, we gave six healthy men an intravenous bolus of human ghrelin (10 microg/kg) or placebo and vice versa 1-2 wk apart in a randomized fashion. Ghrelin elicited a marked increase in circulating GH (15-fold). The elevation of GH lasted longer than 60 min after the bolus injection. Injection of ghrelin significantly decreased mean arterial pressure (-12 mmHg, P < 0.05) without a significant change in heart rate (-4 beats/min, P = 0.39). Ghrelin significantly increased cardiac index (+16%, P < 0.05) and stroke volume index (+22%, P < 0.05). We also examined ghrelin receptor [GH secretagogues receptor (GHS-R)] gene expression in the aortas, the left ventricles, and the left atria of rats by RT-PCR. GHS-R mRNA was detectable in the rat aortas, left ventricles, and left atria, suggesting that ghrelin may cause cardiovascular effects through GH-independent mechanisms. In summary, human ghrelin elicited a potent, long-lasting GH release and had beneficial hemodynamic effects via reducing cardiac afterload and increasing cardiac output without an increase in heart rate.