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Influences of Protein Kinase A and D-Camp on Actin-Myosin Interaction and Energy Consumption of Cardiac Muscles

  • Yasutake Saeki
  • Takakazu Kobayashi
  • Kiyohiro Takigiku
  • Haruo Sugi
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 453)

Abstract

To address controversies concerning the effects of β;-adrenergic stimulation on the rate of myocardial cross-bridge cycling, we measured three mechanical variables, isometric tension development, transient tension response to a step stretch in length (<1% of muscle length), maximum velocity of shortening, and a chemical variable, ATPase activity before and after treatment with the catalytic subunit of protein kinase A (PKA) in demem-branated rat right ventricular trabeculae, and also measured three mechanical variables before and after treatment with D-cAMP in intact ryanodine-induced tetanized preparations. PKA treatment (1 U/μl, 40 min) shifted the pCa-tension relation to the right from 5.41 to 5.26 at pCa50 (the [Ca2+] required for half maximal steady tension) without changing the steepness of the pCa-tension relation and the maximum tension. The rate of the transient tension changes was significantly increased after either PKA or D-cAMP treatment (5 mM, 15 min), regardless of the level of isometric tension. Vmax was increased for a given Ca2+ concentration after either the PKA or D-cAMP treatment, despite the reduced level of isometric tension. The PKA treatment also shifted the pCa-ATPase activity to the right slightly from 5.47 to 5.40 at pCa50, but increased the ATPase activity during a given level of steady isometric tension generation, resulting in an increased tension cost (ATPase activity/tension). These results suggest that, in rat right ventricular trabeculae, β-adrenergic stimulation may increase the rate of cross-bridge cycling by increasing the rate of cross-bridge detachment from actin through a PKA-mediated mechanism, although PKA reduces the Ca2+-sensitivity of the contractile system.

Keywords

ATPase Activity Maximum Tension Isometric Tension Relaxing Solution Tension Cost 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1998

Authors and Affiliations

  • Yasutake Saeki
    • 1
  • Takakazu Kobayashi
    • 2
  • Kiyohiro Takigiku
    • 3
  • Haruo Sugi
    • 2
  1. 1.Department of Physiology School of Dental MedicineTsurumi UniversityTsurumi-ku, Yokohama 230Japan
  2. 2.Department of Physiology School of MedicineTeikyo UniversityTokyo 173Japan
  3. 3.Department of Pediatrics School of MedicineYokohama City UniversityYokohama 230Japan

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