Effect Of Ghrelin On Blood Pressure Of Rats And Contractile Function Of Caodiomyocytes

Ghrelin, secreted from the stomach, stimulates the release of growth hormone. Ghrelin binds to growth hormone secretagogue–receptor (GHSR), cloned from the mammalian pituitary gland. Further studies revealed widespread expression of GHSR in peripheral tissues such as cardiovascular system, indicating that it might have multiple physiological effects. There are still some disputes over its effects on cardiovascular system. Though the research of ghrelin level in healthy obese and lean men and with MRI to analyze the structure and function of heart, Nicholas found that ghrelin had negative effect on RVESV and positive effect on RVEF. Subcutaneous administration of ghrelin can increase cardiac contractility, LVEF and volume ejection, decrease LVESV. On the other side, ghrelin may have direct effect on myocardium. Subcutaneous administration of ghrelin to rats can increase LVEF of dilated cardiomyopathy and growth hormone deficient rat. Recent research suggested that ghrelin decrease contractile function of rat papillary muscles in a concentration-dependent manner. In recent years, the regulate function of ghrelin especially to cardiovascular system has attract great concerns, and suggests that it may have pontential remedy effect to cardiovascular diseases.Our study focused on the effects of ghrelin on the cardiovascular system and its probable mechanism, and tried to discuss the potential clinical value of ghrelin in curing the cardiovascular diseases.The main contents of this study include:1. With drugs given intravenously, heart rate (HR), mean arterial blood pressure (MABP), left ventricular pressure (LVP) and±dp/dtmax were recorded to observe the negative inotropic effects of ghrelin on hearts of rats.2. Investigate the effects of ghrelin on the isolated ventricular myocytes by video-based motion edge-detection system.3. The relaxation effect of ghrelin on abdominal aorta in the rat was studied by means of the isolated abdominal aorta perfusion and the tension of the vessel measurement.Main results:1.Ghrelin(1×10-7~1×10-4 g/kg) can decrease MABP in a dose-dependent way, change LVP insignificantly and has no effect on HR and±dp/dtmax.2. Ghrelin(1×10-9 ~ 1×10-6 mol/L)can decrease PTA and±dL/dtmax in a dose-dependent way.3. Ghrelin(1×10-6 mol/L)had the relaxation effect on rat abdominal aorta. The above-mentioned results suggest:1.Ghrelin has negative inotropic effect.2.Ghrelin(1×10-6 mol/L)had the relaxation effect on rat abdominal aorta.For summary, our study indicated that ghrelin has negative inotropic effect and relaxation effect .