Voltage-gated K+ currents in freshly isolated myocytes of the pregnant human myometrium.
1. Voltage-gated K+ currents in human myometrium are not well characterized, and were therefore investigated, using the whole-cell patch clamp technique, in freshly isolated myometrial smooth muscle cells from pregnant women at term. 2. Three types of voltage-gated K+ currents were identified. IK1 was a 4-aminopyridine-insensitive current with a negative half-inactivation (V0.5 = -61 to -67 mV) and negative activation characteristics (threshold between -60 and -40 mV) and slow kinetics. IK2 was a 4-aminopyridine-sensitive current (half-maximal block at approximately 1 mM) with relatively positive half-inactivation (V0.5 = -30 mV) and activation characteristics (threshold between -40 and -30 mV) and faster kinetics. IK,A was a 4-aminopyridine-sensitive current with a negative inactivation and very fast inactivation kinetics. 3. Both IK1 and IK2 were sensitive to high concentrations of tetraethylammonium (half-maximal block at approximately 3 mM) and low concentrations of clofilium (half-maximal block by 3-10 microM). 4. IK1 and IK2 were unevenly distributed between myometrial cells, most cells possessing either IK1 (30 cells) or IK2 (24 cells) as the predominant current. 5. The characteristics of these currents suggest a possible function in the control of membrane potentials and smooth muscle quiescence in the pregnant human myometrium.
London Myometrial Group and Division of Pharmacology and Therapeutics, King's College London, St Thomas' Campus, Lambeth Palace Road, London SE1 7EH, UK.
G A
GA
Knock
S V
SV
Smirnov
P I
PI
Aaronson
D015761:4-Aminopyridine / Q000494:pharmacology; D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009215:Myometrium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000819:agonists / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011247:Pregnancy; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology
D000889:Anti-Arrhythmia Agents; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D000644:Quaternary Ammonium Compounds; D019789:Tetraethylammonium; C022799:clofilium; D015761:4-Aminopyridine