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AIM: To investigate the influences of electric stimulation applied during the absolute refractory period (ARP) on the cardiac function of normal rabbits and rabbits after myocardial infarction (MI) and to observe the regional effects of this electric stimulation. METHODS: 64 rabbits were randomly assigned to normal and MI groups and each group was then divided into the anterior and posterior groups. A thoracotomy was performed 4 weeks after MI in rabbits. One set of electrodes was inserted into the anterior and posterior wall of left ventricle of the anterior and posterior groups, respectively. Current pulses were delivered during the ARP (called CCM) during sinus rhythm in rabbits. The left ventricular systolic pressure (LVSP) and the left ventricular end diastolic pressure(LVEDP) as well as maximum positive and negative left ventricular pressure change (?dp/dt_(max)) were observed. RESULTS: In the normal and MI groups, LVSP, +dp/dt_(max) significantly increased, and LVEDP, -dp/dt_(max) were reduced during CCM stimulation compared with the baseline (P0.05). CONCLUSION: Electric stimulation delivered during the ARP significantly enhances the contractility and the relaxation of myocardium in normal rabbits and rabbits after MI, and the effects of CCM stimulation on heart are regional. [
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ObjectiveTo investigate the influence of aging and castration on the density of andro gen receptor(AR) in the male rat heart. MethodsAR in the heart of rats aged 40d,90d(intact and castrated) and 2 years were demonstrated by means of immunohistochemical technique and the den sity of the positive staining was measured by using image analys is. The optical density of AR in the septum of the rats were analyzed by anova and doncan process of the SAS data analysis system. Re sultsOD(AR) of the group aged 2 years was higher than that of the groups aged 40d and 90d (0. 3550±0. 0077,0. 31080. 0264 and 0. 3149±0. 0200 respectively), thetwolattergroups showed similarly intensive staining, while the value of castrated group(0. 4136±0. 0320) was signif icantly greater than that of intact same aged group. Conclusion The development of sexual gland has little influence in the density of AR in the male rat heart during prepuberty to adult, both old age and castration increase the density of AR in the rat heart.
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To investigate the influences of bradykinin(BK)on left ventricular hypertrophy and cardiac function in angiotensin-converting enzyme inhibitor(ACEI) therapy in rats after myocardial infarction. METHODS: The effects of enalapril (500 ?g?kg -1 ?d -1 ), enalapril (500 ?g?kg -1 ?d -1 )with BKB 2 receptor antagonist (Hoe-140 500 ?g?kg -1 ?d -1 ), losartan(3 mg?kg -1 ?d -1 ) on left ventricular end-diastolic pressure (LVEDP), maximum positive left ventricular pressure change (+d p /d t max ) and LVW/BW as well as V(m)n of noinfarcted area were examined after 4 weeks treatment in rats after myocardial infarction. RESULTS: The values of LVEDP, LVW/BW and V(m)n of three treatment groups were higher than that of untreated MI group ( P
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AIM: To study the distribution, location and quantity of myocardial collagen(Col) in different phases after myocardial infarction(MI). METHODS: The method of immunohistochemical technique combined with automatic image analysis was used to investigate the changes of collagen Ⅰ and Ⅲ. RESULTS:Contents of Col Ⅰ, Col Ⅲ and the ratio of Ⅰ/Ⅲ were all increased in infarcted area (IA)after MI,and the increase of Col Ⅰ was higher, the collagen fibers still construct a network in acute phase, in chronic stage, all necrosis myocytes were replaced by collagen, the fibers were dense, and paralelled with cardiac cavity surface.In the septum,noninfarcted area, contents of collagen type Ⅰ and Ⅲ, the ratio of Ⅰ/Ⅲ were increased.In acute phase, the increase of type Ⅲ is dominant,with in chronic phase, type Ⅰ is. Right ventricle(RV) has no significant change in acute phase,untill chronic phase,it changed like septum,the increase in collgen is mainly type Ⅰ. CONCLUSION: The collgen remodeled after myocardial infarction were reparative fibrosis in IA phase, and reactive fibrosis in NIA phase. Remodeling occured later in RV than in septum.
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To determine the effects of long term captopril administration on cardiacmorphology and left ventricular function in rats with myocardial infarction, captopril wasadministered to rats 3 days after the begining of myocardial infarction and continued for35 days. Captopril lowened the ratio of left ventricular weight to body weight of bothrats with and without infarction, and also reduced volume, length and dimention of myo-cyte. Captopril had special effects on ventricular geometry in rats with infarction, whichresulted in decreased radius of left ventricular cavity. The cardiac index of captopril-treatedrats with infarction during baseline and a volume loading didn’t change, whereas the ra-dius of left ventricular cavity and LVEDP were decreased significantly, which indicated anincrease of the ejection fraction index. The results showed that long term administrationof captopril might be unfavoralle to compensary myocardial hypertrophy, but catdiacfunction was improved, which was ascribed to reduction of left ventricular cavity volumeand LVEDP.
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We observed the effects of testosterone (T) on myosin ATPase activity and its isoenzyme distribution of noninfarcted myocardium in male infarcted rats. 21 days after myocardial infarction (MI), both myocardial fiber diameter and myosin ATPase activity were increased in T treated MI group when compared with that of the MI group (P
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Plasma A Ⅱ_2 was measured dynamicly by radioimmunoassay in rats after myocardial infarction, and its responses to captopril were studied too. The results showed that after myocardial infarction the concentraction of A Ⅱ rose markedly at first day, but it was sustained briefly and at third day , fell to the level before infarction. Plasma A Ⅱ decreased and was sustained at the almost unchanged level during Long—term captopril administra—tion in rats with infarction.
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Serial observation were made on the variations of plasma testosterone (T) level from 6 hours to 21 days after myocardial infarction (MI) in male and female rats; In the male MI group, plasma T level was reduced by 76% 6 hours after ligation of the left coronary artery. 24 hours after MI, there was a small increase in the T evel, but it was all along significantly lower than preoperative level from 6 hours up to 21 days postoperatively. In the female rats, however, plasma T level was increased by 50% 24 hours postoperatively and returned to the preoperative level 9 days after MI, It is suggested that sex diffe rences in mortality, recovery and compen sation of left ventricular function after MI in the rats might be related to the changes of the plasma T level.