Apelin is an endogenous adipocytokine that plays an important role in the regulation of cardiovascular function. Apelin-36 is a member of apelin family. However cardiac reports related to apelin-36 are very rare. The purpose of this study is to investigate the impact of apelin-36 on hemodynamic variables of the isolated rat hearts.Twenty-eight rats were equally divided into four groups: control, apelin-36 at the following concentrations: 1 nM, 10 nM and 100 nM. The isolated hearts were perfused with modified Krebs-Henseleit solution (mK-Hs) by using the Langendorff method. Cardiac parameters, including left ventricular developed pressure (LVDP), maximal rate of pressure development (+dP/dtmax), heart rate (HR) and coronary flow (CF) were measured. Gene expressions relevant to cardiomyocyte contractility were determined by real-time PCR.10 and 100 nM doses of apelin-36 perfusion led to positive inotropy with an increase of LVDP and +dP/dtmax, which are the indexes of cardiac contractility. Furthermore both doses of apelin-36 increased endothelial nitric oxide synthase (eNOS), sarco/endoplasmic reticulum Ca2+-ATPase (Serca2a) and β2-Adrenergic receptors (β2-AR) mRNA. These results showed that apelin-36 had a positive inotropic effect on the isolated rat heart and can induce eNOS, Serca2a and β2-AR genes activation that enhances contractility of the heart (Tab. 1, Fig. 2, Ref. 23).