Modulation of Ca current during the phosphorylation cycle in the guinea pig heart (original) (raw)

Abstract

The calcium current (I Ca) 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 cell_I_ Ca 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 of_I_ Ca, suggesting their ability to inhibit cAMP-PK. 2) R subunit and PKI, however, reduced basal (i.e. non β-adrenergically stimulated)I Ca only by about 20%. 3) Dialysis with ATPγS resulted in a slow increase in basal_I_ Ca, 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.

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Author notes

1. M. Kameyama
   Present address: National Institute for Physiological Sciences, 444, Okazaki, Japan

Authors and Affiliations

1. II. Physiologisches Institut der Universität des Saarlandes, D-6500, Homburg, Federal Republic of Germany
   M. Kameyama, J. Hescheler & W. Trautwein
2. Physiologische Chemie, Universität des Saarlandes, D-6500, Homburg, Federal Republic of Germany
   F. Hofmann

Authors

1. M. Kameyama
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2. J. Hescheler
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3. F. Hofmann
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4. W. Trautwein
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Additional information

This work was supported by the Deutsche Forschungsgemeinschaft, SFB 38 (Membranforschung), Projekt G, and HO 579/6-2

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Kameyama, M., Hescheler, J., Hofmann, F. et al. Modulation of Ca current during the phosphorylation cycle in the guinea pig heart.Pflugers Arch. 407, 123–128 (1986). https://doi.org/10.1007/BF00580662

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• Received: 02 November 1985
• Accepted: 01 March 1986
• Issue Date: August 1986
• DOI: https://doi.org/10.1007/BF00580662

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