Distinct Hemodynamic Responses to (Pyr)apelin-13 in Large Animal Models.

This study tested the hypothesis that (pyr)apelin-13 dose-dependently augments myocardial contractility and coronary blood flow, irrespective of changes in systemic hemodynamics. Acute effects of intravenous (pyr)apelin-13 administration (10 to 1,000 nM) on blood pressure, heart rate, left ventricular pressure and volume, and coronary parameters were measured in dogs and pigs. Administration of (pyr)apelin-13 did not influence blood pressure ( P = 0.59), dP/d tmax ( P = 0.26), or dP/d tmin ( P = 0.85) in dogs. However, heart rate dose-dependently increased > 70% ( P < 0.01), which was accompanied by a significant increase in coronary blood flow ( P < 0.05) and reductions in left ventricular end-diastolic volume and stroke volume ( P < 0.001). In contrast, (pyr)apelin-13 did not significantly affect hemodynamics, coronary blood flow, or indexes of contractile function in pigs. Furthermore, swine studies found no effect of intracoronary (pyr)apelin-13 administration on coronary blood flow ( P = 0.83) or vasorelaxation in isolated, endothelium-intact ( P = 0.89) or denuded ( P = 0.38) coronary artery rings. Examination of all data across (pyr)apelin-13 concentrations revealed an exponential increase in cardiac output as peripheral resistance decreased across pigs and dogs ( P < 0.001; R2 = 0.78). Assessment of the Frank-Starling relationship demonstrated a significant linear relationship between left ventricular end-diastolic volume and stroke volume across species ( P < 0.001; R2 = 0.70). Taken together, these findings demonstrate that (pyr)apelin-13 does not directly influence myocardial contractility or coronary blood flow in either dogs or pigs. NEW & NOTEWORTHY Our findings provide much needed insight regarding the pharmacological cardiac and coronary effects of (pyr)apelin-13 in larger animal preparations. In particular, data highlight distinct hemodynamic responses of apelin across species, which are independent of any direct effect on myocardial contractility or perfusion.