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Apelin Tatemoto in 1998 using reverse pharmacology extracted from cow stomach secretions vasoactive peptide, is the G-protein coupled receptor APJ receptor (a putative receptor protein related to THE angiotensinII receptor AT1) the endogenous ligand. Apelin gene located on the X chromosome q25-26.1, contains three exons and two introns. Apelin precursor protein consisting of 77 amino acids, can be hydrolyzed to generate a different length of the active peptides, such as apelin-36, apelin-31, apelin-17, apelin-13. , Apelin and its receptor APJ in the body is widely distributed in the central and peripheral tissues, such as the heart, lungs, kidneys, central nervous system, adipose tissue, regulation of the cardiovascular system homeostasis, salt and water balance, regulating the role of the immune response, is an important physiological regulatory peptides. Cardiovascular tissue, apelin enhance myocardial contractility, diastolic blood vessels, lower blood pressure, suggesting that the peptide may be an important cardiovascular regulatory peptide. Single rat ventricular myocytes, the work as a model, the application of the whole-cell patch clamp technique to observe apelin-13 in rat ventricular myocytes sodium-calcium exchange current (I Na / Ca ), L-type calcium current mechanism of ion channel current (of the I Ca, L ), ATP-sensitive potassium channel current (IK ATP ), in order to further clarify the apelin's positive inotropic effect on the heart . The aim of the present study was to investigate apelin-13 in acutely isolated rat ventricular myocytes positive inotropic effect of ion channel mechanisms. Methods Male Sprague-Dawley rats (250-300 g), intraperitoneal anesthesia were decapitated quick whichever cardiac, collagenase solution is perfused heart, the pending heart softened clip ventricular portion, Shredded pipetting make separation into a single ventricular myocytes. Ventricular myocytes using the whole-cell patch-clamp technique I Na / Ca , I Ca, L , the IK ATP . Administration group containing different concentrations of apelin-13 cells in an outer perfusion ventricular muscle cells for 5 min; control group directly to the extracellular fluid perfusion for 5 min, to record and to observe the changes in the current curve. Results of 1.Apelin-13 on rat ventricular myocytes I Na / Ca Apelin-13 on the inward, outward I Na / Ca have increased the role. Concentration of 0.01 nmol / L, 0.1 nmol / L, 1 nmol / L apelin-13 in the forward INaCa respectively than before administration increased 20 ± 4% (P lt; 0.05, n = 8), 33 ± 7% (P lt; 0.01, n = 8), 54 ± 10% (P lt; 0.01, n = 8), to make reverse I Na / Ca were increased by 1 ± 6% (P gt After being; 0.05, n = 8), 7 ± 2% (P lt; 0.01, n = 8), 30 ± 7% (P lt; 0.01, n = 8), control group treated with extracellular fluid 5 min, The reverse I Na / Ca not 5 ± 4% and 2 ± 7% reduction. Of 2.Apelin-13 on myocardial cell I Ca, L impact Apelin-13 in a concentration-dependent increase of rat cardiomyocytes I Ca, L to apelin- 13 concentrations were 0.01 nmol / L, 0.1 nmol / L, 1 nmol / L extracellular fluid perfusion myocardial cells after 5 min I Ca, L , respectively, increases of 3 ± 3%, 20 ± 6 %, 45 ± 9% in the control group due to the the rundown phenomenon of decreases 5 ± 5%, 0.1 nmol / L, 1 nmol / L group and the control group compared to a significant difference (P lt; 0.01, n = 8), 0.01 nmol / L, and the control group had no significant difference (P gt; 0.05, n = 8). 1 nmol / L of apelin-13 perfused 5 min after the IV curve was significantly down, but does not change I Ca, L voltage dependence and reversal potential. Control I Ca, L activation curve half-activation potential is -19.43 ± 2.76mV, the slope is 4.76 ± 0.33 mV, 1 nmol / L for 5 min perfusion apelin-13 semi-active potential becomes -18.93 ± 3.05 mV, the slope becomes 5.21 ± 0.38 mV, no significant difference (P GT both; 0.05, n = 6). Control I Ca, L loss of inactivation curves half inactivation potential is -23.62 ± 1.79mV slope is 5.35 ± 0.21 mV, 1 nmol / L apelin-13 perfused 5 min after the half-inactivation potential becomes -24.6 ± 2.14 mV, the slope becomes 5.47 ± 0.23, no significant difference (P GT both; 0.05, n = 6). The above results indicate that apelin-13 increases I Ca, L role not by changing the L-type calcium channel activation and inactivation gating characteristics. The 3.Apelin-13 IK ATP of records from 50 mV to -100 mV for 125 ms ramp stimulation of myocardial cells IK the ATP . 1 nmol / L, 10 nmol / L of apelin-13 can not make the current increase in the current give pinacidil significantly increased, and can be blocked glibenelmaide (The current the IK ATP ) prompt apelin-13 resting myocardial cells can not make ATP-sensitive potassium channel opener. The conclusion of this work as a model single rat ventricular myocytes, whole-cell patch clamp technique, the study found, apelin-13 concentration-dependent increase the ventricular muscle cells I of Na / Ca and I Ca, L , the ATP-sensitive potassium channels open role. The above results indicate that apelin-13 on cardiac positive inotropic effect mechanism of ion channel currents may increase of myocardial cells I Na / Ca and of the I Ca, L Current thereby increasing myocardial cells calcium influx.
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