Ca2+ clearance mechanisms in isolated rat adrenal chromaffin cells.
1. Intracellular Ca2+ clearance mechanisms were studied in rat adrenal chromaffin cells, by measuring slow tail currents through small-conductance Ca(2+)-activated K+ channels and using indo-1 photometry following depolarization-induced Ca2+ loading. 2. Following several-hundred millisecond depolarizations, [Ca2+]i decayed in three phases. An initial fast decay was followed by a long-lasting, low plateau, then [Ca2+]i returned to the resting level slowly. 3. Replacement of external Na+ moderately slowed [Ca2+]i decay, indicating a contribution of plasma membrane Na(+)-Ca2+ exchange. 4. Raising external pH or application of extracellular Eosin of La3+ prolonged slow tail currents, indicating a contribution of plasma membrane Ca(2+)-ATPase to Ca2+ clearance. 5. Ca(2+)-induced Ca2+ release from caffeine-sensitive stores occurred during depolarization. 6. Inhibition of endoplasmic reticulum Ca(2+)-ATPase had little effect on Ca2+ clearance. 7. Slow tail currents and [Ca2+]i decay following 0.2 - 2 s depolarizations were much prolonged by mitochondrial inhibition with carbonyl cyanide m-chlorophenylhydrazone (CCCP) or Ruthenium Red, which abolished the initial rapid decay and plateau of [Ca2+]i. 8. In conclusion, mitochondrial Ca2+ uptake plays a major role in Ca2+ clearance by rapidly and reversibly sequestering Ca2+ during depolarization-evoked Ca2+ loads.
Park
Y B
YB
Department of Physiology and Biophysics, University of Washington, School of Medicine, Seattle 98195-7290, USA.
Herrington
J
J
Babcock
D F
DF
Hille
B
B
D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002469:Cell Separation; D019439:Chromaffin Cells / Q000378:metabolism*; D004594:Electrophysiology; D004721:Endoplasmic Reticulum / Q000201:enzymology; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology; D051381:Rats; D012430:Ruthenium Red / Q000494:pharmacology; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D015221:Potassium Channels; D019831:Sodium-Calcium Exchanger; D012430:Ruthenium Red; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000252:Calcium-Transporting ATPases; D002118:Calcium