Potassium currents in freshly dispersed myometrial cells.
K+ currents in freshly dispersed cells from rat myometrium at estrus were studied with the patch-clamp technique (whole cell). Three types of K+ currents were identified: 1) a fast-activating current (IKf), 2) a slowly activating current (IKs), and 3) a transient current (IKt). IKf had a half-activation voltage of 12 mV and a time constant of activation (tau on) of approximately 3 ms at +50 mV. IKs had a tau on of approximately 9 ms at +50 mV and a half-activation potential of 33 mV. Both IKf and IKs were sustained and became potentiated by the entrance of Ca2+ from the patch pipette. These two Ca(2+)-activated K+ currents were inhibited by 100 nM external charybdotoxin and were blocked by external tetraethylammonium (TEA, 2-20 mM). The third current (IKt) was transient, had a faster tau on (approximately 1 ms), and a decay phase with a time constant of approximately 8 ms at +50 mV. This current had a half-activation potential of 22 mV. IKt was not potentiated by intracellular Ca2+, was sensitive to 4-aminopyridine (1 mM), was insensitive to external charybdotoxin (100 nM) and TEA (2 mM), and spontaneously decreased with time.
Piedras-Rentería
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Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Stefani
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Toro
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D000818:Animals; D002118:Calcium / Q000502:physiology; D018999:Charybdotoxin; D003584:Cytological Techniques; D004594:Electrophysiology; D004971:Estrus; D005260:Female; D009215:Myometrium / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D012604:Scorpion Venoms / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D012604:Scorpion Venoms; D013757:Tetraethylammonium Compounds; D018999:Charybdotoxin; D019789:Tetraethylammonium; D011188:Potassium; D002118:Calcium