Properties and molecular basis of the mouse urinary bladder voltage-gated K+ current.
Potassium channels play an important role in controlling the excitability of urinary bladder smooth muscle (UBSM). Here we describe the biophysical, pharmacological and molecular properties of the mouse UBSM voltage-gated K+ current (IK(V)). The IK(V) activated, deactivated and inactivated slowly with time constants of 29.9 ms at +30 mV, 131 ms at -40 mV and 3.4 s at +20 mV. The midpoints of steady-state activation and inactivation curves were 1.1 mV and -61.4 mV, respectively. These properties suggest that IK(V) plays a role in regulating the resting membrane potential and contributes to the repolarization and after-hyperpolarization phases of action potentials. The IK(V) was blocked by tetraethylammonium ions with an IC50 of 5.2 mM and was unaffected by 1 mM 4-aminopyridine. RT-PCR for voltage-gated K+ channel (KV) subunits revealed the expression of Kv2.1, Kv5.1, Kv6.1, Kv6.2 and Kv6.3 in isolated UBSM myocytes. A comparison of the biophysical properties of UBSM IK(V) with those reported for Kv2.1 and Kv5.1 and/or Kv6 heteromultimeric channels demonstrated a marked similarity. We propose that heteromultimeric channel complexes composed of Kv2.1 and Kv5.1 and/or Kv6 subunits form the molecular basis of the mouse UBSM IK(V).
Thorneloe
Kevin S
KS
Department of Pharmacology, College of Medicine, University of Vermont, Burlington 05405, USA.
Nelson
Mark T
MT
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D051668:Delayed Rectifier Potassium Channels; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D051669:Shab Potassium Channels; D019789:Tetraethylammonium / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology / Q000502:physiology*; D014549:Urinary Incontinence / Q000503:physiopathology
D051668:Delayed Rectifier Potassium Channels; C496990:Kcnb1 protein, mouse; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels; D019789:Tetraethylammonium; D015761:4-Aminopyridine