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Pflügers Archiv

, Volume 407, Issue 2, pp 123–128 | Cite as

Modulation of Ca current during the phosphorylation cycle in the guinea pig heart

  • M. Kameyama
  • J. Hescheler
  • F. Hofmann
  • W. Trautwein
Excitable Tissues and Central Nervous Physiology

Abstract

The calcium current (ICa) in the heart is increased by phosphorylation of a protein which is part of, or close to, the Ca channel. The phosphorylation is catalysed by cAMP-dependent protein kinase (cAMP-PK). The question whether dephosphorylated channels are available to open on depolarization was examined in ventricular myocytes of guinea pig by recording whole cellICa during dialysis with either regulatory (R) subunit of cAMP-PK or protein kinase inhibitor (PKI) or adenosine-5′-(γ-thio)-triphosphate (ATPγS). The following results were obtained: 1) R subunit reduced and PKI reversed the isoprenaline (ISP)-induced enhancement ofICa, suggesting their ability to inhibit cAMP-PK. 2) R subunit and PKI, however, reduced basal (i.e. non β-adrenergically stimulated)ICa only by about 20%. 3) Dialysis with ATPγS resulted in a slow increase in basalICa, presumably due to dephosphorylation-resistant thiophosphorylation. 4) When, however, the cell was dialyzed with PKI the effect of ATPγS was almost completely suppressed, suggesting no detectable phosphorylation related to the channel activity in this condition. These results support the view that even in the dephosphorylated state Ca channels are available to open on depolarization and that phosphorylation by cAMP-PK increases the opening probability.

Key words

Guinea pig heart Ca current Phosphorylation cycle 

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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • M. Kameyama
    • 1
  • J. Hescheler
    • 1
  • F. Hofmann
    • 2
  • W. Trautwein
    • 1
  1. 1.II. Physiologisches Institut der Universität des SaarlandesHomburgFederal Republic of Germany
  2. 2.Physiologische ChemieUniversität des SaarlandesHomburgFederal Republic of Germany

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