Basic Research in Cardiology

, Volume 84, Issue 3, pp 282–290

Sensitivity to oxidants of mitochondrial and sarcoplasmic reticular calcium uptake in saponin-treated cardiac myocytes

  • T. Kaminishi
  • K. J. Kako
Original Contributions

DOI: 10.1007/BF01907975

Cite this article as:
Kaminishi, T. & Kako, K.J. Basic Res Cardiol (1989) 84: 282. doi:10.1007/BF01907975

Summary

Calcium transport functions of mitochondria and sarcoplasmic reticulum (SR) were studied without prior extraction using isolated rat heart myocytes permeabilized with saponin. Calcium uptake by SR was rapid and its affinity was high in comparison to calcium uptake by mitochondria, which had a higher capacity. The sensitivity of uptake to two oxidants, H2O2 and HOCl (hypochlorous acid), depended on the cytosolic calcium concentration; when this was similar to the concentration in diastole (180 nM), HOCl inhibited calcium uptake by mitochondria and SR, whereas when the calcium concentration was 750 nM, mitochondrial calcium uptake showed relatively high resistance, although SR uptake was still markedly inhibited by HOCl. Calcium uptake of both mitochondria and SR was less sensitive to the action of H2O2 than to HOCl, and the H2O2 effect was less dependent on the cytosolic calcium concentration. Therefore, HOCl, when produced by activated leukocytes and supplied to the heart cells, may seriously impair the excitation-contraction coupling function of SR, whereas H2O2, possibly generated directly by mitochondria or generated from superoxide anions, may be tolerated relatively well by heart SR and mitochondria.

Key words

calcium uptake cardiomyocyte cytosol hydrogen peroxide hyperchlorous acid mitochondria permeabilizedcell saponin sarcoplasmic reticulum 

Abbreviations

CCCP

carbonyl cyanide m-chlorophenylhydrazone

EGTA

ethylene glycol bis[beta-aminoethylether]tetraacetic acid

HEPES

N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid

HOCl

hypochlorous acid

SR

sarcoplasmic reticulum

Copyright information

© Dr. Dietrich Steinkopff Verlag 1989

Authors and Affiliations

  • T. Kaminishi
    • 1
  • K. J. Kako
    • 1
  1. 1.Department of Physiology, Faculty of Health SciencesUniversity of Ottawa, School of MedicineOttawaCanada