| Objective: Currently, coronary artery disease has become one of the main disease of harming the human's health, especially acute myocardial infarction (AMI). After AMI occurs, larger area of myocardial infarction often leads to left ventricular systolic and diastolic dysfunction and evolves into congestive heart failure. Recent reseach found that the activation of neurohormonal system after AMI has a crucial effect on the evolvement of AMI into congestive heart failure. The moderate activation can mitigate the bad change of hemodynamics that occurs because of myocardial infarction and left ventricular systolic and diastolic dysfunction, so that the blood pressure becomes steady and the important apparatus are provided enough blood stream. However, the excessive activation leads to the apoptosis of cardiac muscle cells and the ventricle remodeling ,so that the excessive activation and the latter two progresses form a bad cycle that make the heat after AMI become congestive heart failure.Therefore, the reseach on the activation and the progress law of neurohormonal system after AMI have a significance on the diagnosis and treatment about the disease. As two important members of neurohor-monal system, BNP and endothelium function have important and particular action on Cardiovascular system. We designed this study to find the evolvements of brain natriuretic peptide(BNP), entothelin-1(ET-1) and nitrogen monoxide(NO) serum levels in rats after AMI and observe the effects of the captopril on the evolvements in order to offer new theories for the diagnosis and treatment about AMI.Methods: 30 male wistar rats weighting about 250g,about from 13 to 16 week-ages,were used in our study. Before operation the rats were randomly divided into three groups:①sham group (n=10) ;②AMI group (n=10) ;③AMI+capt group (AMI+captopril,n=10). Operation course: First injected 10% Chloral Hydrate to every rat's abdominal cavity according to 35mg/kg.After narcosis they were fixed on an operation stage. Sent a thin tube into the glottis of trachea and connected it to a ventilator. It was a certificate to put the tube successfully that the rat's stethidium rose and fell with the respiratory rate of the ventilator.Set the breath parameters.After careful disinfection to surgical incision with 75% alcohols, the heart was exposed through a 1.0~1.5cm left lateral thoracotomy. Broke the pericardium, extruded the heart quickly and exposed the left ventricular dissociative wall. After the left coronary artery was found lying between the left artial appendage and the pulmonary artery taper, the anterior desecending artery was ligated at about 2-3mm below the beginning part of left coronary artery with the 6-0 size silk thread. The ligation deep was 0.3-0.5mm. After the heart was laid back and the gas was drawn out, the thorax was closed.The ligation step needed about 30 second. It was thought of a successful ligation that the infracted part became white during operation. Oversewed all layers of muscle and skins and removed the ventilator. In the sham group rats, just a thoracotomy was made, a ligation was not. After operation the rats needed presevate them heat and be laid in a single cage. After regaining consciousness, the rats were again weighed in and numbered. Whereafter, thay were divided into three groups and laid in different cages and fed. The above operation must be carried through under the sistuation that have no germ. After operation the muscle injecting with ampicillin according to 2×105 U/d for 5 days prevented the infection. Strictly keeping to the protocol ensured the ligation part and time and other conditions consistentDissolve captopril in 1ml water according to 10mg per kilogram after operation.Then the rat was injected quickly. From next day on captopril (50 mg/kg) dissolved in 2ml water was given through gastric tube every morning, whereas the sham group was given equal physiological saline water.1-ml blood samples were obtained the sixth hour after operation;every 6 hours during the first 24 hours;thereafter once a day within the first week;and in the second week. Blood sampling from the third day through the second week was done at 8:00AM. Blood samples were taken from the rat's vein and placed into tubes. A centrifugal machin was used to rotate at 3000r/min speed in 10 minute in order to separate the serum from the blood.The serum was transferred into centrifugal tubes that were adhibited tags with group numbers, rat numbers and times.Thereafter, the serum immediately was stored at -80℃until analysis.Rat's serum concentrations of BNP and ET-1 both were measured with an enzyme-linked immunosorbent assay(ELISA). Reagents were purchased from American Rapidbio(RB) corporation.Their measurement instrument was the TECAN from the clinical laboratory of the first hospital of Hebei medical university. Rat's serum concentrations of NO was measured with a nitrate reductase colorimetry. Reagents of NO were purchased from Nanjing Jiancheng Bioengineering Institute. It's measurement instrument was the 721 spectrophotometer from the clinical laboratory of the first hospital of Hebei medical university.SPSS 13.0 software pack was used to make statistical analysis. The serum levels of BNP, ET-1 and NO were compared over the time course using ANOVA for repeated measures. Where the F value was found to be significant, the data were compared with Student-Newman-Keuls tests. One-Way ANOVA was used in order to compare the datas from sham group,AMI group and AMI+capt group at a specific time. Where the F value was found to be significant, the datas were compared with Student-Newman-Keuls tests. All values were expressed as mean±SEM. Statistical significance was defined as P<0.05.Results:1 Comparison About Serum Levels of BNP, ET-1 and NO in Rat From Sham Group,AMI Group and AMI+capt Group1.1 At every time, there all was a sginificant difference in the serum levels of BNP and ET-1 from AMI group,AMI+capt group and sham group.Compared with AMI group, the serum levels of BNP and ET-1 at every time in AMI+capt Group and sham group both was smaller(P<0.05).Similarly, compared with AMI+capt group, the serum levels of BNP and ET-1 at every time in sham group was also smaller(P<0.05).1.2 At every time, there all was a sginificant difference in the serum levels of NO between AMI group and AMI+capt group and between AMI group and sham group. Compared with AMI group, the serum levels of NO at every time in AMI+capt group and sham group both was bigger(P<0.05). At every time before the 7th day, there all was a sginificant difference in the serum levels of NO between AMI+capt group and sham group. Compared with AMI +captopril group, the serum levels of NO at every time in AMI +captopril group and sham group both was bigger till the 7th day(P<0.05).In the 7th day and the 14th day, there was no sginificant difference between AMI+capt group and sham group(P7d=0.164, P14d=0.678).2 Time Course of Serum Levels of BNP, ET-1 and NO in Rat From Sham Group,AMI Group and AMI+capt Group2.1 The serum BNP level in AMI group rat had two peak values. Whenas, the serum BNP level in AMI+capt group rat had one peak value. The first peak of the serum BNP level in AMI group rat was higher and earlier than that of AMI+capt group rat. The serum BNP level in sham group rat was smoother. (Fig.1)2.2 The serum ET-1 level in AMI group rat and AMI+capt rat both had one peak value. The peak of the serum ET-1 level in AMI group rat was higher and earlier than that of AMI+capt group rat. The serum ET-1 level in sham group rat was smoother. (Fig.2)2.3 The serum NO level in AMI group rat and AMI+capt rat both had one bottom value. The bottom of the serum NO level in AMI group rat was lower and earlier than that of AMI+capt group rat. The serum NO level in sham group rat was smoother. (Fig.3)Conclusions:1 Compared with sham group rat, the serum levels of BNP and ET-1 at every time in AMI group rat both was higher; by contraries, the serum levels of NO was lower. This showed that the increase of BNP and ET-1 serum levels and the decrease of NO serum level participated in the progress of AMI.2 Compared with AMI group rat, the serum levels of BNP and ET-1 at every time in AMI+capt group rat both was lower; by contraries, the serum levels of NO was higher. This showed that the captopril could lessen the increase of BNP and ET-1 serum levels and the decrease of NO serum level and was beneficial to the progress of AMI.3 In AMI group rat, the serum BNP level had two peaks: the first peak at 12.6±0.60 hours and the second peak at 153.60±7.33 hours after operation. Thereafter, the level decreased gradually but was still higher in the 14th day than that of sham group rat. The serum ET-1 level in AMI group rat increased after operation, forming a peak of 272.12±1.27pg/ml at 7.8±0.92 hours. Thereafter, the level decreased gradually but was still higher in the 14th day than that of sham group rat. The serum NO level in AMI group rat decreased after operation, forming a bottom of 16.98±0.35μmol/L at 11.4±0.60 hours. Thereafter, the level increased gradually but was still lower in the 14th day than that of sham group rat.4 Based on the peak value and the forming time of the peak of the serum BNP and ET-1 serum levels, and based on the bottom value and the forming time of the bottom of NO serum level in AMI+capt group rat, it was more shown that the captopril could restrain the activation of neurohormonal system and was better beneficial to the progress of AMI. |
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