Abstract
In adult skeletal muscle, G-proteins have been shown to modulate the calcium channels both directly and through a cAMP-dependent phosphorylating mechanism. We have investigated the action of G-proteins on the L-type calcium current in cultured rat muscle cells (myoballs) under voltage clamp in whole cell or perforated patch modes. Intracellular photolytic release of 200 microM GTP gamma S inhibited the L-type calcium current. Inclusion of 500 microM uncaged GTP gamma S in the patch pipette in the whole cell configuration reduced the calcium current by a similar amount. Under perforated patch conditions external application of 10 microM of the beta-adrenergic agonist isoproterenol also reduced the calcium current. Pretreatment of the cells with pertussis toxin reversed the effect of GTP gamma S and removed that of isoproterenol. We conclude that rat myoballs contain beta-adrenergic receptors that inhibit the L-type calcium current, and that this inhibition is mediated by a pertussis toxin-sensitive G-protein.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / analogs & derivatives
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Adenosine Triphosphate / pharmacology
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Adenosine Triphosphate / radiation effects
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Animals
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Calcium / metabolism*
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Calcium Channels / drug effects*
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Cell Differentiation
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GTP-Binding Proteins / antagonists & inhibitors
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GTP-Binding Proteins / metabolism
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Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology*
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Guanosine Triphosphate / analogs & derivatives
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Guanosine Triphosphate / pharmacology
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Guanosine Triphosphate / radiation effects
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Ion Channel Gating / drug effects*
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Isoproterenol / pharmacology*
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Muscles / cytology
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Muscles / drug effects*
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Pertussis Toxin
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Photolysis
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Rats
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Rats, Wistar / metabolism
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Receptors, Adrenergic, beta / drug effects
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Receptors, Adrenergic, beta / physiology*
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Thionucleotides / pharmacology
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Thionucleotides / radiation effects
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Virulence Factors, Bordetella / pharmacology
Substances
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1-(2-nitro)phenylethyl-P(3)-guanosine 5'-O-(3-thio)triphosphate
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Calcium Channels
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Receptors, Adrenergic, beta
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Thionucleotides
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Virulence Factors, Bordetella
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Guanosine 5'-O-(3-Thiotriphosphate)
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P(3)-1-(2-nitro)phenylethyladenosine 5'-triphosphate
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Guanosine Triphosphate
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Adenosine Triphosphate
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Pertussis Toxin
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GTP-Binding Proteins
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Isoproterenol
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Calcium