Slow inactivation of cardiac L-type Ca2+ channel induced by cold acclimation of guinea pig.
Whole cell L-type Ca2+ current was recorded in ventricular myocytes dissociated from guinea pigs that were bred at ambient temperatures ranging between daily averages of 4 and 29 degrees C. The dynamic voltage range of inactivation, as measured using 400-ms conditioning pulses and a holding potential of -40 mV, extended from -50 to -20 mV in myocytes prepared in summer. In winter, the inactivation curve was shifted to more negative potentials than in summer. Double-pulse experiments revealed that the negative shift was due to slow-inactivation kinetics. The negative shift of inactivation could be induced in myocytes prepared from animals that had been kept at 5 degrees C for > 3 wk in the summer. The negative shift in Ca2+ current inactivation could be abolished by adding guanosine 5'-O-(2-thiodiphosphate) (5 mM) to the pipette solution, but not by adding staurosporine (2 microM) or 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (100 microM) to the bath. The cold acclimation may introduce the slow inactivation of the cardiac L-type Ca2+ channel through an unknown pertussis toxin-insensitive G protein.
Takagi
S
S
Department of Physiology, Kyoto University Graduate School of Medicine, Japan.
Kihara
Y
Y
Sasayama
S
S
Mitsuiye
T
T
D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D003080:Cold Temperature; D004553:Electric Conductivity; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology; D007700:Kinetics; D037342:Pertussis Toxin; D012621:Seasons; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D015220:Calcium Channels; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D037342:Pertussis Toxin; D019204:GTP-Binding Proteins