DI-4-ANEPPS CAUSES PHOTODYNAMIC DAMAGE TO ISOLATED CARDIOMYOCYTES

Action potential recordings from isolated guinea pig ventricular cells in the whole-cell recording mode were used to study the toxic and pho todynamic properties of the voltage-sensitive fluorescent dye di-4-ANE PPS. Staining of the cardiomyocytes with di-4-ANEPPS (30 or 60 mu M; 1 0 min) did not alter the action potential shape. When the stained cell s were illuminated (1W/cm(2)) severe effects on the action potential w ere observed. There was prolongation of the action potential duration, occurrence of early afterdepolarizations, reduction of the membrane r esting potential and eventually inexcitability. Addition of the antiox idant catalase (100 IU/ml) to the extracellular solution delayed the o nset of these effects, suggesting that reactive-oxygen-intermediates t ake part in di-4-ANEPPS induced photodynamic damage. Since di-4-ANEPPS is a very important tool for optical membrane potential recordings in heart tissue and single cardiomyocytes catalase might be useful in su ppressing photodynamic damage during optical potential recordings.