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 clamped cells, Calcium release from the s,r. (whether occurring spontaneously or evoked by caffeine) produced changes of membrane current which could 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 the Ca-activated Cl current decayed more quickly than did Na-Ca exchange, Possible explanations for the different kinetics of these two Ca-sensitive currents are discussed.