Ionic currents in single smooth muscle cells of the human vas deferens.
OBJECTIVE
Smooth muscle cells of the vas deferens have an important role in carrying sperms to the exterior but little is known of their electrophysiological properties. We characterized the voltage-gated ion channel currents in single smooth muscle cells of the human vas deferens (HVSMCs).


METHODS
We observed contractile responses of 8 circular smooth muscle strips of the human vas deferens to a high concentration (10 mM) of tetraethylammonium. HVSMCs were isolated using proteolytic enzymes (collagenase and papain), and were used for an electro-physiological study using whole cell and inside-out patch clamp configurations.


RESULTS
The application of 10 mM tetraethylammonium induced rhythmic contractions of the strips. When HVSMCs were dialyzed with a KCl solution, step depolarizations of membrane potential evoked oscillatory outward K currents that were not inactivated. The large conductance Ca activated K (BKCa) and delayed rectifier components of the outward current were identified. The BKCa channel showed a large single channel conductance (162.7 +/- 13.2 pS with 5 mM K in the patch pipette). Two types of Ca currents were identified in the whole cell configuration. With a cell held at -50 mV an L-type Ca current was present during a depolarizing step pulse. From a holding potential of -90mV L-type and T-type Ca currents were elicited by depolarizing step pulses.


CONCLUSIONS
HVSMCs have 2 (L and T) types of Ca channels and 2 types of K (BKCa and delayed rectifier) channels. Voltage dependent changes of these ion channels and their interactions may be important in regulating vas contractility.
Park
So Young
SY
Department of Physiology, College of Medicine, Chung-Ang University, Seoul, South Korea.
Lee
Moo Yeol
MY
Keum
Eun Mi
EM
Myung
Soon Chul
SC
Kim
Sae Chul
SC
D000328:Adult; D015220:Calcium Channels / Q000502:physiology*; D020746:Calcium Channels, L-Type / Q000502:physiology; D020747:Calcium Channels, T-Type / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000166:cytology*; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology; D014649:Vas Deferens / Q000166:cytology* / Q000502:physiology*
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated