Ion-channel currents of smooth muscle cells isolated from the prostate of guinea-pig

Authors


Dr Sung Joon Kim, Assistant Professor, Sungkyunkwan University School of Medicine, Suwon 440–746, Korea.
e-mail: sjoonkim@med.skku.ac.kr

Abstract

OBJECTIVE

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

MATERIALS AND 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 µmol/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).

CONCLUSION

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.

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