FCCP MODULATION OF CA2+ OSCILLATION IN RAT MEGAKARYOCYTES

The effects of a mitochondrial uncoupler, FCCP, (carbonyl cyanide-p-tr ifluromethoxyphenyl-hydrazone on the regulation of cytoplasmic Ca2+ we re investigated in ATP-induced Ca2+ oscillation system of rat megakary ocyte. Application of FCCP did not induce any detectable Ca2+-activate d K+ current (I-KCa) but pretreatment with FCCP modulated the ATP-indu ced repetitive I-KCa. FCCP abolished the I-KCa induced by low concentr ations of ATP. However, when the concentration of ATP was high, the un coupler also changed the periodic current to a sustained one. Similar biphasic regulation by the uncoupler was observed in the case of IP3-e voked repetitive I-KCa. These results indicate that FCCP inhibits both Ca2+ mobilization and elimination processes after IP3 liberation indu ced by agonist stimulation.