CA-ACTIVATED CHLORIDE CURRENT AND NA-CA EXCHANGE HAVE DIFFERENT TIMECOURSES DURING SARCOPLASMIC-RETICULUM CA RELEASE IN FERRET VENTRICULAR MYOCYTES

The aim of this work was to measure membrane currents activated by Ca release from the cardiac sarcoplasmic reticulum (s.r,), Intracellular Ca concentration ([Ca2+](i)) was measured using fluo-3 in patch clampe d cells, Calcium release from the s,r. (whether occurring spontaneousl y or evoked by caffeine) produced changes of membrane current which co uld be separated into a Ca-activated Cl current which was inhibited by DIDS or Cl removal and a Na-Ca exchange current, Both these currents had different time courses from the measured [Ca2+](i). Furthermore th e Ca-activated Cl current decayed more quickly than did Na-Ca exchange , Possible explanations for the different kinetics of these two Ca-sen sitive currents are discussed.