Effects Of Spironolactone And Losartan On Ventricular Remodeling And Ventricular Function After Coronary Microembolization In Rats

ObjectivesThe aim of this study was to establish a model of coronary microembolization (CME) in rats by the use of the autogeneic microthrombotic particles, and to explore the evidences of myocardial and ventricular remodeling and ventricular function impairment following CME, to investigate possible molecular mechanisms involved in myocardial and ventricular remodeling, and to observe whether Spironolactone was able to regress or diminish ventricular remodeling and impairment produced by CME, and to observe whether Spironolactone plus Losartan regresses or diminishes ventricular remodeling and impairment more than Losartan only does.MethodsWe created a rat model of CME by injecting a suspension of microthrombotic particles into left ventricle when clamping the ascending aorta. The microthrombotic particles were generated from the rat clots. Sixty rats were randomly divided into 5 groups, each consisted of 10 rats: control group(CL), sham-operation group(SO), CME model group(ME), and Spironolactone intervention group(SP), Losartan intervention group(LO) and Spironolactone plus Losartan intervention group(SL). The animals were sacrificed at 4 weeks after CME. A microscopy incorporated with an image analysis software (ImagePro-4) was employed to calculate the number of micro-myocardial infarction (Nmmi) in sections with HE-staining, to measure the collagen volume fraction (CFV) in sections with Marsson-staining. Radioimmunoassay was conducted to assess the levels of angiotensinⅡ(AngⅡ) and aldosterone (ALD), immunohistochemistry to detect the expressions of TNF-α, IL-1, and activated NFκB(IOD) in myocardial tissue, and spectrophotometer to analyse concentration of NO. And serial echocardiography was performed to monitor alterations of left ventricular end-systolic and end-diastolic diameter (LVESD, LVEED), and left ventricular short-axis fraction shortening(LVFS) and ejection fraction(LVEF) , and physiologicography to document the changes of left ventricular systolic pressure (LVSP) and end-diastolic pressure pressure(LVEDP), and left ventricular maximum positive and negative dp/dt (±LVdp/dtmax).Results1. Validation of model of CME28 days after operation: compared with sham group, both CFV and Nmmi were increased in model group (P<0.01,each), but no significant difference between sham group and control group (P>0.05); compared with sham group, both LVEDD and LVESD were increased in model group (P<0.01), but LVPWT, LVFS and LVEF were reduced(P<0.01,each); compared with sham group, both LVSP and±LVdp/dtmax were reduced in model group.(P<0.01, each), LVEDP was increased (P<0.01), but no significant difference between sham group and control group (P>0.05).2. Changes of neuroendocrine-cytokine system in model of CME28 days after operation, compared with sham group, the expressions of TNF-α, IL-1, activated NFκB(IOD) in myocardial tissue were increased and the level of NO was decreased in model group (P<0.01,each).3. Effects of Spironolactone during chronic phase of CME.28 days after operation: compared with model group, the expressions of TNF-α, IL-1β, activated NFκB(IOD) in myocardial tissue were decreased and the level of NO was increased in spironolactone group; LVEDD and LVESD become smaller with higher LVEF in spironolactone group (P<0.01,each); LVSP and±LVdp/ dtmax were increased and LVEDP was decreased in spironolactone group(P<0.05,each).4. Effects of Spironolactone plus Losartan and Losartan only on CME.28 days after operation: compared with Losartan intervention group, the expressions of TNF-α, IL-1, activated NFκB(IOD) in myocardial tissue were decreased and the level of NO was increased in Spironolactone lus Losartan intervention group, LVEDD and LVESD were smaller with higher LVEF in Spironolactone plus Losartan intervention group(P<0.01,each). LVSPand±LVdp/ dtmax were increased and LVEDP was decreased in Spironolactone plus Losartan intervention group(P<0.05,each)Conclusions1. The model of CME in rats was established by the use of the autogeneic microthrombotic particles successfully.2. At chronic stage of CME, the neuroendocrine-cytokine system activates, leading to myocyte losing, interstitial collagen fiber proliferation, and then ventricular remodelling and dysfunction.3. Spironolactone inhibits the activation of the neuroendocrine-cytokine system, reduces inflammatory reaction and oxidative stress reaction. These beneficial effects ultimately translate to improve ventricular function.4. Spironolactone plus Losartan intervention further inhibits neuroendocrine- cytokine activation, inflammatory and oxidative stress reaction, and thus more significantly improves ventricular function.