REMODELING OF EXTRACELLULARLY RECORDED ACTION POTENTIALS OF RAT HEART SUBEPICARDIAL CARDIOMYOCYTES AFTER ISCHEMIA REPERFUSION INJURY

Abstract

A number of systemic heart diseases leading to the development of heart failure (aortic stenosis, hypertension, diabetic cardiomyopathy, reperfusion injury etc.) are accompanied by a pronounced reorganization of the T-system of cardiomyocytes, both in humans and animals. However, structural-functional changes within this membrane compartment of cardiomyocytes following ischemia-reperfusion (IR) have not been thoroughly studied. The aim of the work was to study the remodeling of the T-system in the subepicardial cardiomyocytes of the left ventricle of the rat heart after IR injury using confocal microscopy and extracellular recording methods. The study was carried out after 24 hours, two weeks, and four weeks following IR. A remodeling of action potentials, recorded extracellularly in the cardiomyocyte membrane patches devoid of t-tubule entrances (type 1 eAP), was observed. Starting from 24 hours up to 4 weeks after IR, there was an increase in the duration of their decline time (T90) and the formation of eAP after-hyperpolarization phase, reaching maximum values by the fourth week after IR. A decrease in the second peak’s amplitude of eAPs, measured from cardiomyocyte surface locations with t-tubule openings, was also noticed four weeks after IR. In this investigation, no observable changes in the structural organization of the T-system were found. These data suggest that functional modifications of the epicardial cardiomyocyte T-system after IR injury may precede its structural modifications.