中文摘要：

目的研究心肌梗死（MI）后心脏局部不同部位的B受体分布情况。方法14只健康杂种犬，随机分为MI组（7只）与假手术对照组（7只），结扎冠状动脉前降支造成MI模型。术后4周应用组织多普勒超声技术检测梗死区近端心底部及远端心尖部与梗死区比邻的非梗死区心肌组织运动速度，静脉推注美托洛尔后重复测定，观察β受体阻滞剂对上述部位组织运动的抑制作用；应用RT-PCR技术检测上述部位β1、β2受体mRNA表达情况。结果MI组心底及心尖侧的组织运动速度比正常对照组均有所降低，B受体阻滞剂干预后组织运动的抑制作用低于正常对照组，在心尖部尤其明显，可见该部位B受体密度减低。RT-PCR显示MI组心底部及心尖部β1受体mRNA表达量（0．78±0．02、0．41±0．02）低于正常对照组（0．82±0．03、0．85±0．04），心底部降低程度明显低于心尖部，差异有统计学意义（P〈0．05）；正常对照组心底与心尖之间的表达量无统计学差异。β2受体的mRNA表达量无显著变化。结论MI后心脏局部存在β1受体mRNA表达量的区域性变化，而β2受体无明显异常，这就造成心尖部β1、β2受体比例发生明显改变。

英文摘要：

Objective To investigate the distribution of β-adrenoceptors at different sites of heart after myocardial infarction（MI）. Methods 14 dogs were randomly divided into 2 equal groups ： MI group, undergoing ligation of the left anterior descending coronary artery, and control group undergoing sham-operation. Four weeks later metoprolol, a β1-adrenergic receptor antagonist, was injected intravenously. Doppler tissue imaging （DTI） was used to evaluate the peak systolic myocardial velocity （Sm） of the regions apical and basal to the infarction region before and after the injection. Then the dogs were killed with their hearts taken out. Reverse-transcriptase polymerase chain reaction was used to examine the mRNA expression of β1-receptor and β2-receptor in the non-infracted myocardial tissues apical and basal to the infarction region. Results The Sm values at the regions apical and basal to the infarction region of the MI group were 3.93 ±0. 47 and 0. 81 ± 0. 19 cm/s respectively, both significantly lower than those of the control group （ 10.84 ± 1.97 and 5.85 ± 1.15 cm/s respectively, both P 〈 0.05）. After injection of metoprolol, the Sm values at the regions apical and basal to the infarction region of the MI group were 3.43 ± 0.37 and 0.73 ± 0. 14 cm/s respectively, not significantly different from those before the injection; however, the corresponding Sm values of the control group were 8.69 ± 1.14 and 4.33 ± 0.29 cm/s respectively, both significantly lower than those before the injection （ both P 〈 0.05 ）. The mRNA expression levels of β- receptor decreased in both apical and basal regions in the MI group compared with those in the control group, and the degree of expression decrease at the apical region was significantly greater than that at the basal region. However, there was no significant difference in the expression level of β1-receptor mRNA between the apical and basal regions in the control group. There was no significant difference in the mRNA.expression of β2-recept