糖尿病大鼠膈肌功能损伤及钙调控蛋白基因表达的改变

目的研究糖尿病大鼠膈肌功能及钙调控蛋白基因表达的变化，探讨糖尿病大鼠膈肌功能损伤的发生机制。方法使用链
脲佐菌素建立糖尿病大鼠模型，SD大鼠随机分为糖尿病组（随机血糖≥16.7 mmol/L）和正常对照组，造模后4周、8周测定大鼠
体质量和膈肌/体质量比值，生化指标检测各组大鼠空腹血糖和膈肌组织线粒体琥珀酸脱氢酶（SDH）活性；应用体外灌流大鼠
膈肌条的方法，测定单收缩张力、最大强直张力、峰值收缩时间、半舒张时间、张力-频率曲线，电镜观察大鼠膈肌超微结构，采用
RT-PCR检测大鼠膈肌肌质网钙泵（SERCA）和受磷蛋白（PLB）mRNA表达。结果（1）与正常对照组相比，糖尿病大鼠体质量和
膈肌质量/体质量比值均明显降低（P<0.01），膈肌组织SDH的活性显著降低（P<0.01）；（2）在给予大鼠膈肌条10、20、40、60、
100 Hz刺激时，糖尿病大鼠膈肌在各频率下的收缩张力明显低于正常对照组（P<0.01）；膈肌力学指标单收缩张力和最大强直张
力明显降低，峰值收缩时间和半舒张时间明显延长（P<0.01）；（3）超微结构显示糖尿病组大鼠膈肌组织损伤明显，肌纤维断裂，
肌质网扩张，线粒体水肿，数目减少，脊断裂，空泡化或囊泡化，同时可见随病程延长膈肌损伤明显加重；（4）RT-PCR结果提示：
与正常对照组相比，糖尿病组大鼠膈肌SERCA mRNA表达均明显降低（P<0.01），糖尿病大鼠膈肌SERCA mRNA表达8周组比
4周组明显降低（P<0.01），糖尿病大鼠膈肌PLB mRNA表达显著增强（P<0.01）。结论糖尿病大鼠膈肌超微结构受到破坏，线
粒体损伤和数目减少，线粒体SDH活性降低，ATP生成减少，膈肌组织SERCA mRNA表达减少和PLB mRNA表达增强，引起
膈肌肌质网摄取Ca2+减少，促成膈肌收缩和舒张功能损伤。

Diaphragm dysfunction and expressions of calcium regulatory proteins in diabetic rats

Objective To study the changes in diaphragmatic function and gene expressions of calcium regulatory proteins in
diabetic rats and explore the mechanism of diaphragm dysfunction in diabetes mellitus. Methods SD rats were randomly
divided into normal control group and diabetic (induced by intraperitoneal STZ injection) group. After 4 and 8 weeks, the
body weight and diaphragm to body weight ratio were measured, and the activities of succinic dehydrogenase (SDH) in the
diaphragm and blood glucose were assayed. The diaphragm contractility was assessed and the alterations of diaphragm
ultrastructure were observed. RT-PCR was used to detect the changes in sarcoplasmic reticulum Ca2 +-ATPase (SERCA) and
phospholamban (PLB) mRNA expressions in the diaphragm. Results The diabetic rats showed a significant weight loss with a
lowered diaphragm to body weight ratio (P<0.01) and SDH activity (P<0.01). The peak twitch tension and maximum tetanic
tension of the diaphragm were significantly lowered and the time to peak contraction and half relaxation time significantly
prolonged (P<0.01) in the diabetic rats, which also exhibited a lowered tetanic force in response to stimulus (P<0.01).
Transmission electron microscopy revealed obvious ultrastructural changes of the diaphragm in diabetic rats. RT-PCR showed
significantly decreased SERCA and increased PLB mRNA expressions in diabetic rat diaphragm (P<0.01), and these changes
intensified with time (P<0.01). Conclusions Diabetes can cause impairment of diaphragmatic ultrastructure, mitochondrial
injuries, and lowered SDH activity and ATP production. Decreased SERCA and increased PLB mRNA expressions in diabetes
result in reduced Ca2+ uptake by the diaphragm sarcoplasmic reticulum to induce diaphragm dysfunction.