2-DIMENSIONAL MILLISECOND ANALYSIS OF INTRACELLULAR CA2-SCANNING CONFOCAL MICROSCOPY - INCREASE IN AMPLITUDE BY ISOPROTERENOL( SPARKS IN CARDIAC MYOCYTES BY RAPID)

Two dimensional images of myocardial Ca2+ sparks, non-propagating loca l rises in cytoplasmic Ca2+ concentration, were obtained at 4 msec int ervals with a rapid-scanning confocal laser microscope, Nikon RCM 8000 , and fluo-3. Spontaneous Ca2+ sparks were observed at apparently rand om sites throughout the cytoplasm of rat ventricular cells. The durati on of sparks was 30 to 40 msec and the time to peak intensity about 10 msec, Ryanodine (1 mu M) completely inhibited Ca2+ sparks while nicar dipine (3 mu M) had no effect. Isoproterenol (1 mu M) had no effect on the frequency and distribution of Ca2+ sparks but significantly incre ased their amplitude. These results suggest that myocardial Ca2+ spark s are the result of spontaneous release of Ca2+ from the sarcoplasmic reticulum and that p-adrenergic stimulation may result in functional m odification of the ryanodine receptor channel. (C) 1997 Academic Press .