Biomolecules & Therapeutics

The Korean Society of Applied Pharmacology (한국응용약물학회)
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Enhancement of Ca2+ Current Does Not Regulate the Speed of Depolarization-induced Ca2+ Propagation Wave in Rat Atrial Myocytes

  • Woo, Sun-Hee (College of Pharmacy, Chungnam National University) ;
  • Hwang, Seon-Hwa (College of Pharmacy, Chungnam National University) ;
  • Kim, Joon-Chul (College of Pharmacy, Chungnam National University) ;
  • Morad, Martin (Department of Pharmacology, School of Medicine, Georgetown University)
  • Published : 2007.12.31
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Abstract

In atrial myocytes, lacking t-tubules, $Ca^{2+}$ current ($I_{Ca}$)-initiated $Ca^{2+}$ release at the peripheral junctional sites propagates into the interior of the cell by diffusion of $Ca^{2+}$. We have previously reported that time of activation of the central sites is independent of $I_{Ca}$. In the present study we have probed the effects of Bay K 8644 on $Ca^{2+}$ propagation wave to the center of the myocyte using rapid 2-D confocal $Ca^{2+}$ imaging in the rat atrial myocytes. Enhancement of $I_{Ca}$ by Bay K 8644 accelerated the rate of peripheral $Ca^{2+}$ release, but did not affect the speed of propagation of central release. In contrast, enhancement of $I_{Ca}$ by intracellular cAMP reduced the magnitude of peripheral and central $Ca^{2+}$ transients, but significantly accelerated the speed of central $Ca^{2+}$ release. Our data suggest that the speed of central $Ca^{2+}$ propagation triggered by $I_{Ca}$ is not regulated by the magnitude of either $I_{Ca}$ or local cytosolic $Ca^{2+}$ releases.

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References

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