Shigematsu S, Maruyama T, Kiyosue T, Arita M
Department of Physiology, Oita Medical University, Japan.
Heart Vessels. 1994;9(6):300-6. doi: 10.1007/BF01745095.
We examined the characteristics of the action potentials of single ventricular myocytes obtained from the hearts of rats with chronically-induced diabetes. Male Wistar rats were made diabetic by injecting streptozotocin (65 mg/kg) and 30-32 weeks later the hearts were excised and used for an electrophysiological study. Action potentials were recorded from isolated right ventricular myocytes by an electrode fabricated for patch clamp in the whole-cell recording configuration. The action potential durations (APDs) of steady state chronic diabetic rat myocytes were longer than those of age-matched normal rat myocytes at all levels of repolarization (APD25, APD50, APD75, and APD90). As the stimulation frequency was increased (0.2-2 Hz), the APDs were lengthened in both diabetic and normal rats, and the difference of APDs between the groups was greater when the stimulation frequency was higher. When we examined alterations of APDs under conditions of train stimulation (2Hz, 20 stimuli), (1) the APDs in both groups were prolonged, and (2) the degree of prolongation of APD was significantly greater and the rate of APD prolongation was significantly faster in myocytes from the diabetic rats. The prolongation of APD in these heart cells is probably secondary to alteration of the transient outward current Ito, and sheds light on repolarization abnormality in cases of diabetic cardiomyopathy.
我们研究了从慢性诱导糖尿病大鼠心脏获取的单个心室肌细胞动作电位的特征。雄性Wistar大鼠通过注射链脲佐菌素（65mg/kg）制成糖尿病模型，30 - 32周后切除心脏用于电生理研究。采用膜片钳全细胞记录模式下制作的电极，从分离的右心室肌细胞记录动作电位。在所有复极化水平（APD25、APD50、APD75和APD90），稳态慢性糖尿病大鼠心肌细胞的动作电位时程（APD）均长于年龄匹配的正常大鼠心肌细胞。随着刺激频率增加（0.2 - 2Hz），糖尿病大鼠和正常大鼠的APD均延长，且刺激频率越高，两组之间APD的差异越大。当我们在串刺激条件下（2Hz，20个刺激）检测APD的变化时，（1）两组的APD均延长，（2）糖尿病大鼠心肌细胞的APD延长程度显著更大，且APD延长速率显著更快。这些心脏细胞中APD的延长可能继发于瞬时外向电流Ito的改变，这为糖尿病性心肌病的复极化异常提供了线索。
