Effects of diabetic cardiomyopathy on regional electrophysiologic characteristics of rat ventricle.
OBJECTIVE
To identify the possible causes of the lengthening of the action potential duration described in patients affected by diabetes mellitus.


METHODS
We studied the effects of streptozotocin-induced diabetes on the current density of the repolarising potassium currents It(o), IK, Iss and IK1 in enzymatically isolated myocytes from three different regions of rat heart: total right ventricle, subepicardium at the apex of the left ventricle and subendocardium at the base of the left ventricle.


RESULTS
No changes in IK1 were found due to diabetes, but there was a uniform decrease in It(o) (50%) and Iss (40%) current densities in the three regions. In contrast, IK diminished unevenly, with the greatest decrease in the subendocardium at the base of the left ventricle (48%), followed by the subepicardium at the apex of the left ventricle (32%) and right ventricle (10%).


CONCLUSIONS
These findings suggest the existence of regional differences in ion channel expression associated with diabetes. The decrease of these repolarising currents could account for the lengthening of action potential and the consequent change in the Q-T interval of the ECG observed in diabetic rats.
Casis
O
O
University of the Basque Country, School of Pharmacy, Department of Physiology, Bilbao, Spain.
Gallego
M
M
Iriarte
M
M
Sánchez-Chapula
J A
JA
D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D009202:Cardiomyopathies / Q000209:etiology / Q000503:physiopathology*; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000150:complications / Q000503:physiopathology*; D004562:Electrocardiography; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology / Q000473:pathology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D019789:Tetraethylammonium / Q000494:pharmacology; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right
D015221:Potassium Channels; D019789:Tetraethylammonium; D015761:4-Aminopyridine