Ca2+ clearance mechanisms in isolated rat adrenal chromaffin cells

J Physiol. 1996 Apr 15;492 ( Pt 2)(Pt 2):329-46. doi: 10.1113/jphysiol.1996.sp021312.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adrenal Glands / cytology
  • Adrenal Glands / metabolism*
  • Animals
  • Calcium / metabolism*
  • Calcium / physiology
  • Calcium-Transporting ATPases / metabolism
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone / pharmacology
  • Carrier Proteins / metabolism
  • Cell Membrane / metabolism
  • Cell Separation
  • Chromaffin Cells / metabolism*
  • Electrophysiology
  • Endoplasmic Reticulum / enzymology
  • Male
  • Mitochondria / metabolism
  • Potassium Channels / physiology
  • Rats
  • Ruthenium Red / pharmacology
  • Sodium-Calcium Exchanger


  • Carrier Proteins
  • Potassium Channels
  • Sodium-Calcium Exchanger
  • Ruthenium Red
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone
  • Calcium-Transporting ATPases
  • Calcium