Acidosis facilitates spontaneous sarcoplasmic reticulum Ca2+ release in rat myocardium

C. H. Orchard, S. R. Houser, A. A. Kort, A. Bahinski, M. C. Capogrossi, E. G. Lakatta

Research output: Contribution to journalArticle

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Abstract

Prvious studies have shown that acidosis increases myoplasmic [Ca2+](Ca(i)). We have investigated whether this facilitates spontaneous sarcoplasmic reticulum (SR) Ca2+ release and its functional sequelae. In unstimulated rat papillary muscles, exposure to an acid solution (produced by increasing the [CO2] of the perfusate from 5 to 20%) caused a rapid increase in the mean tissue Ca(i), as measured by the photoprotein aequorin. This was paralleled by an increase in spontaneous microscopic tissue motion caused by localized Ca2+ myofilament interactions, as monitored in fluctuations in the intensity of laser light scattered by the muscle. In regularly stimulated muscles, acidosis increased the size of the Ca2+ transient associated with each contraction and caused the appearance of Ca(i) oscillations in the diastolic period. In unstimulated single myocytes, acidosis depolarized the resting membrane potential by ~5 mV and enhanced the frequency of spontaneous contractile waves. The small sarcolemmal depolarization associated with each contractile wave increased and occasionally initiated spontaneous action potentials. In regularly stimulated myocytes, acidosis caused de novo spontaneous contractile waves between twitches; these waves were associated with a decrease in the amplitude of the subsequent stimulated twitch. Ryanodine (2 μM) abolished all evidence of spontaneous Ca2+ release during acidosis, markedly reduced the acidosis-induced increase in aequeorin light, and reduced resting tension. We conclude that acidosis increases the likelihood for the occurrence of spontaneous SR Ca2+ release, which can (a) cause spontaneous action potentials, (b) increase resting tension, and (c) negatively affect twitch tension.

Original languageEnglish
Pages (from-to)145-165
Number of pages21
JournalJournal of General Physiology
Volume90
Issue number1
Publication statusPublished - 1987

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Sarcoplasmic Reticulum
Acidosis
Myocardium
Muscle Cells
Action Potentials
Luminescent Proteins
Aequorin
Light
Ryanodine
Muscles
Papillary Muscles
Myofibrils
Membrane Potentials
Lasers
Acids

ASJC Scopus subject areas

  • Physiology

Cite this

Orchard, C. H., Houser, S. R., Kort, A. A., Bahinski, A., Capogrossi, M. C., & Lakatta, E. G. (1987). Acidosis facilitates spontaneous sarcoplasmic reticulum Ca2+ release in rat myocardium. Journal of General Physiology, 90(1), 145-165.

Acidosis facilitates spontaneous sarcoplasmic reticulum Ca2+ release in rat myocardium. / Orchard, C. H.; Houser, S. R.; Kort, A. A.; Bahinski, A.; Capogrossi, M. C.; Lakatta, E. G.

In: Journal of General Physiology, Vol. 90, No. 1, 1987, p. 145-165.

Research output: Contribution to journalArticle

Orchard, CH, Houser, SR, Kort, AA, Bahinski, A, Capogrossi, MC & Lakatta, EG 1987, 'Acidosis facilitates spontaneous sarcoplasmic reticulum Ca2+ release in rat myocardium', Journal of General Physiology, vol. 90, no. 1, pp. 145-165.
Orchard CH, Houser SR, Kort AA, Bahinski A, Capogrossi MC, Lakatta EG. Acidosis facilitates spontaneous sarcoplasmic reticulum Ca2+ release in rat myocardium. Journal of General Physiology. 1987;90(1):145-165.
Orchard, C. H. ; Houser, S. R. ; Kort, A. A. ; Bahinski, A. ; Capogrossi, M. C. ; Lakatta, E. G. / Acidosis facilitates spontaneous sarcoplasmic reticulum Ca2+ release in rat myocardium. In: Journal of General Physiology. 1987 ; Vol. 90, No. 1. pp. 145-165.
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