Endogenous DHP-sensitive Ca(2+) channels in Pleurodeles oocytes.
The double electrode voltage-clamp technique was used to study voltage-dependent Ca(2+) channels in Pleurodeles oocytes. From a holding potential of -80 mV, Ba-current (IBa) (recorded in Cl-free solution, Ba(2+ = 40 mM) activated at -36.7 +/- 4 mV, peaked at -11.6 +/- 4 mV and reversed at 55 +/- 7 mV (n = 24). This current activated slowly (rise time was 0.98 +/- 0.2 s;n = 14 at -10 mV) and was not inactivated. Cadmium (Cd(2+), 500 microM) completely inhibited I(Ba). The effect of Cd(2+) was dose-dependent (EC(50) = 37 +/- 5 microM; n = 5). Moreover, IBa was insensitive to omega-conotoxin (10 microM) but interestingly this I(Ba) displayed dihydropyridine (DHP) sensitivity. Bay K 8644 (5 microM), a DHP activator, increased the peak current amplitude in a dose-dependent manner (EC(50) = 5.9 +/- 0.6 microM; n = 10) and shifted the threshold and the maximum of current/voltage relationship towards negative potentials by -10 mV. Nifedipine (5 microM), a DHP antagonist, decreased I(Ba) by 80% at HP of -80 mV (EC(50) = 1.2 +/- 0.2 microM; n = 6). We concluded that Pleurodeles oocytes possess High-Voltage Activated Ca(2+) channels with properties similar to L-type Ca(2+) channels.
Ouadid
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Laboratoire de Physiologie Cellulaire, Université des Sciences et Technologies, Villeneuve d'Aseq, France.
Browaeys-Poly
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Vilain
J P
JP
Guilbault
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P
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D004095:Dihydropyridines / Q000494:pharmacology*; D008564:Membrane Potentials; D008978:Mollusk Venoms / Q000737:chemistry; D009543:Nifedipine / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism* / Q000502:physiology; D010455:Peptides / Q000494:pharmacology; D010999:Pleurodeles / Q000378:metabolism*; D020866:omega-Conotoxin GVIA
D015220:Calcium Channels; D004095:Dihydropyridines; D008978:Mollusk Venoms; D010455:Peptides; D001464:Barium; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C038806:1,4-dihydropyridine; D020866:omega-Conotoxin GVIA; D009543:Nifedipine; D002118:Calcium