IONIC CURRENTS IN SINGLE SMOOTH MUSCLE CELLS OF THE HUMAN VAS DEFERENS

Purpose: 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). Materials and 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 (BK Ca ) and delayed rectifier components of the outward current were identified. The BK Ca 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 (BK Ca and delayed rectifier) channels. Voltage dependent changes of these ion channels and their interactions may be important in regulating vas contractility.