Effects of hypoxia, acidosis, and simulated ischemia on repriming of caffeine contracture in rat myocardium

Motoyoshi Shimizu, Shinichi Kimura, Robert J. Myerburg, Arthur L. Bassett

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

This study was designed to examine the effects of hypoxia, acidosis, glucose-free medium and their combination on contraction and sarcoplasmic reticulum (SR) function in rat ventricular trabeculae. The isometric twitch tension was measured during superfusion with hypoxic (PO2 < 30 mmHg), acidic (pH 6.80), glucose-free, or their combined ("ischemic") Tyrode's solution at 20°C. The time needed to fully recover the contraction induced by 10 mm caffeine (repriming time) was measured to indirectly estimate the Ca2+ uptake of the SR. In "ischemia" and acidosis, the peak developed tension decreased progressively for the first 30 min (37.6 ± 9.2% and 56.6 ± 8.4% of control at 30 min, respectively), and then became steady. In hypoxic solution, the peak developed tension decreased moderately for the first 30 min (86.8 ± 4.8% of control at 30 min), and thereafter remained steady. Developed tension did not change significantly during 60 min of superfusion with glucose-free solution. The repriming time of caffeine contraction was significantly delayed in both "ischemic" and hypoxic solutions, but was unchanged in acidic and glucose-free solutions. These results lead us to suggest that depressed SR function to accumulate Ca2+ may contribute to the decline in tension in ischemia and hypoxia, but that other mechanisms are important in the tension decline induced by acidosis.

Original languageEnglish (US)
Pages (from-to)697-705
Number of pages9
JournalJournal of Molecular and Cellular Cardiology
Volume22
Issue number6
DOIs
StatePublished - Jun 1990

Keywords

  • Acidosis
  • Caifeine
  • Contractile function
  • Hypoxia
  • Sarcoplasmic reticulum

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

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