Ion-channel currents of smooth muscle cells isolated from the prostate of guinea-pig.
OBJECTIVE
To characterize the voltage-activated ion-channel currents in guinea-pig prostate smooth muscle cells (GPSMCs).


METHODS
GPSMCs were isolated using collagenase, and used in a whole-cell patch clamp study.


RESULTS
When GPSMCs were dialysed with a CsCl solution all the outward K+ currents were blocked and the step-like depolarization (holding voltage -70 mV) of the cell membrane evoked inward currents that were completely blocked by nifedipine (1 micromol/L). With KCl solution, step depolarizations showed outward K+ currents composed of fast, transient outward current (Ito) and outward currents that did not inactivate. Ito was resistant to a high concentration of tetraethylammonium (TEA, 5 mmol/L) but was blocked by 4-aminopyridine (5 mmol/L). The half-activation and half-inactivation voltages of Ito were 6 mV and -58 mV, respectively. With low Ca2+ buffer (0.1 mmol/L EGTA) in the solution, there were spontaneous transient outward currents (STOCs) at depolarized membrane voltages (0 mV). STOCs were blocked by TEA (1 mmol/L) or iberiotoxin (10 nmol/L) but were insensitive to apamin (100 nmol/L).


CONCLUSIONS
This voltage-clamp study showed that GPSMCs have l-type Ca2+ channels and more than two types of K+ channels. The voltage- and time-dependent changes of these ion channels and their interactions might be important in forming action potentials and regulating contractility.
Oh
S-J
SJ
Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea.
Kim
K M
KM
Chung
Y-S
YS
Hong
E-K
EK
Shin
S Y
SY
Kim
S J
SJ
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D006168:Guinea Pigs; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011467:Prostate / Q000502:physiology*
D002121:Calcium Channel Blockers; D007473:Ion Channels; D026902:Potassium Channel Blockers; D011189:Potassium Chloride