抄録
Diabetes mellitus (DM) frequently accompanies with contractile dysfunction and arrhythmia. L-type Ca2+ channel current (ICa(L)), transient outward current (Ito), delayed rectifier outward K+ current (IK(delay)) and Na/Ca exchanger current (INCX) in ventricular myocytes were compared between control (LETO) and a type II DM model (OLETF) rats using a patch-clamp technique at 50 weeks of age to clarify electrophysiologic changes in diabetic heart. Blood pressure (BP) was measured at caudal artery by noninvasive tail-cuff method. After rats were anesthetized by sodium pentobarbital, electrocardiogram (ECG) was recorded by apex-base lead, and then hearts were excised and perfused with collagenase solution to isolate myocytes. Fibrosis of ventricles was histologically evaluated using Azan stain and connexin 43 protein (Cx43) expression was quantitated by western blot. Systolic and diastolic BPs were significantly elevated in OLETF rats. PQ interval and QRS duration were significantly prolonged and the cell sizes of myocytes were enlarged remarkably in OLETF rats. Current densities of (ICa(L), Ito, IK(delay) and INCX were not changed in OLETF rats as compared with those in LETO rats. Although fibrosis was not seen in OLETF rat ventricles, Cx43 expression significantly decreased. We thought that the QRS duration was prolonged due to the delay in conduction of excitation in OLETF rat ventricles, which might be related with the decrease in Cx43 expression. [J Physiol Sci. 2006;56 Suppl:S105]
