Intercellular Ca2+ waves in rat heart muscle.
1. Confocal laser scanning microscopy was used to visualize intercellular transmission of Ca2+ waves in intact rat ventricular trabeculae micro-injected with the calcium indicator fluo-3. 2. Ca2+ waves usually failed to be transmitted from cell to cell. At identified individual end-to-end cell contacts, successful transmission interspersed with failure, which sometimes occurred despite an apparent small spritz of Ca2+ between cells. The probability of cell to cell transmission (Ptran) was 0.13. 3. Ca2+ waves arose preferentially near junctions of connected cells, where connexin-43 was found, but randomly in enzymatically disconnected heart cells. 4. beta-Adrenergic stimulation significantly increased Ptran (to 0.22) and heptanol, an uncoupler of gap junction channels, significantly decreased it (to 0.045). 5. In regions of high [Ca2+]i due to damage, wave frequency decreased markedly with each cell-cell junction passed. 6. The Ca2+ permeability of cardiac gap junctions may be regulated, and the low ability of cardiac gap junctions to transmit Ca2+ may help control the spread of Ca2+ from damaged regions.
Departments of Physiology and Medicine, School of Medicine, University of Maryland, 655 West Baltimore Street, Baltimore, MD 21201, USA.
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Lamont
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Luther
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Balke
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Wier
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002450:Cell Communication / Q000502:physiology; D017630:Connexins / Q000378:metabolism; D005456:Fluorescent Dyes; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism; D006321:Heart / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011914:Rats, Inbred BN; D014475:Uncoupling Agents / Q000494:pharmacology; D014966:Xanthenes
D000318:Adrenergic beta-Agonists; D000814:Aniline Compounds; D017630:Connexins; D005456:Fluorescent Dyes; D014475:Uncoupling Agents; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium