不同类型长期心脏超负荷大鼠心肌β1-肾上腺素能受体mRNA表达与左心收缩功能变化

【目的】检测长期心脏超容量（volumeoverload，VOL）、压力超负荷（pressure overload，POL）大鼠左心室收缩功能、心肌岛-肾上腺素能受体（β1-adrenergic receptor，β1-AR）maNA表达及去甲肾上腺素（nompinephrine，NE）含量变化。【方法】建立大鼠动静脉瘘-VOL、腹主动脉缩窄-POL及假手术对照组，于术后不同时间点检测左心室收缩压（LVSP）、舒张末压（LVEDP）及dP／dtmax、dP／dtmax用Northern杂交检测各时间点心肌β1-ARmRNA表达水平，实验结束时检测心肌NE含量。【结果】VOL后3dLVSP低于假手术对照组24％（P〈0．05），此后逐渐增高，60d高于对照组32．8％（P〈0．05），LVEDP3～30d高于假手术组178％～235％（P〈0．05）；POL后LVSP逐渐增高，14～60d高于对照组21．1％～39．2％（P〈0．05），LVEDP190．6％～464．2％（P〈0．05），60d2组LVEDP均恢复至对照组水平（P〉0．05）。与对照组比较VOL大鼠3～30dβ1-ARmRNA无明显下降（P〉0．05），60d下降50％（P〈0．05）；POL大鼠β1-ARmRNA表达3d下降68％（P〈0．05），14d74％（P〈0．05），30d86％（P〈0．05），60d下降94％（P〈0．05）；与对照组比较，VOL大鼠dP／dtmax、dP／dtmin除术后30d与对照组相近（P〉0．05），其余时间点均降低（P〈0．05），POL大鼠术后3d降低（P〈0．05），此后逐渐增高，60d高于对照组（P〈0．05）；两种心脏超负荷动物心肌NE含量均下降（P〈0．05），POL较VOL大鼠下降更为明显（P〈O．05）。【结论】长期心脏POL较VOL对左心室重量、收缩功能及心肌NE含量影响不同，心肌β1-AR表达水平变化规律亦不同，这些变化说明：（1）可能与二种超负荷后心脏交感神经功能不同变化有关。（2）-定时间内代偿性心肌肥厚对维持心室收缩功能发挥主要作用。（3）心肌β1-AR表达降低可能对减轻NE的不良作用、维持心功能有益。

Expression of β1 - adrenergic receptor mRNA and left ventricular contractile function in rats with chronic pressure versus volume overload

Objective] To characterize that the temporal responses in cardiac performance and myocardial β1 - adrenergic receptor （β1- AR） expression and norepinephrine （NE） content secondary to the chronic pressure （POL） and volume overloads （VOL） respectively induced by superiorrenal aortic constriction （AC） and an infrarenal arteriovenous fistula （AVF） in rats.Methods] LV systolic （LVSP） and end-diastolic pressure （LVEDP）, weight, contractile function （i.e., dP/dtmax and dP/dtmax in vivo）, β1 - AR mRNA levels and the NE content were assessed at 3, 14, 30 and 60 days post- AVF and AC compared with age - matched control animals. Results] In the two groups LV weight （LVW） was increased identically compared with normals, however, the hypertrophic response was much greater in POL （ P 〈 0.05） but left ventricular wt （mg） to body wt （g） ratio （LV/BW） marginally greater in the POL vs VOL group （ P 〉 0.05）. In two groups LVSP was consistently increased, it was lower in VOL group in early phase after operation compared with POL and control group, LVEDP of the groups was elevated markedly initially and subsequently declined to a control value at 60 days after the operation. LV contractility, as assessed by dP/dtmax and dP/dtmax, in POL group was gradually increased and higher compared with the control （ P 〈 0.05）, however, in VOL group was lower except 30 days after AVF. In VOL group myocardial β1 - AR mRNA level did not decreased from 3 to 30 d, until 60 d after the operation （ P 〈 0.05）, in contrast, in POL group the β1 - AR mRNA level decreased sharply by 68.4%, 7d.3%, 86.2% and 93.6% （P 〈 0.05） at each time point after the operation. At the end, the NE content was lower in the groups compared with the control （ P 〈 0.05）, and that in POL group was lower than VOL group （ P 〈 0.05）. Conclusions] Current data showed hearts exposed to pressure and volume overload displayed different physiopathological features. The longterm card