Voltage-operated Ca(2) (+) currents and Ca(2) (+) -activated Cl(-) currents in single interstitial cells of the guinea-pig prostate.
OBJECTIVE
To investigate the expression of 'T-type' and 'L-type' voltage-operated Ca(2) (+) channels in single interstitial cells of the guinea-pig prostate.


METHODS
Whole-cell and perforated patch-clamp techniques were applied to prostatic interstitial cells (PICs) dispersed using collagenase.


RESULTS
In contrast to prostatic myocytes, PICs under voltage clamp and filled with K(+) (130 mm) were distinguished by the absence of a voltage-operated transient outward K(+) current or spike discharge upon membrane depolarisation when under current clamp. Depolarisation of Cs(+) -filled PICs evoked an inward current at potentials positive to -60 mV, which peaked in amplitude near 0 mV. This inward current increased when Ba(2+) (5 mm) replaced the external Ca(2) (+) (1.5 mm) and displayed a variable sensitivity to the inhibitory actions of conditioning depolarisations to -40 mV applied before the test depolarisation or to 1 μm nifedipine, the 'L-type' Ca(2) (+) channel blocker. A residual inward current recorded in nifedipine was blocked by 10 μm Ni(2) (+) . Cs(+) -filled PICs also displayed a slowly inactivating outward current that was little affected by nifedipine, reduced by the Cl(-) channel blocker, niflumic acid (10 μm) and blocked by Ba(2) (+) or a conditioning depolarisation.


CONCLUSIONS
PICs express both a small 'T-type' Ca(2) (+) channel current (ICa ) and a large 'L-type' ICa . Ca(2) (+) influx through 'T-type' ICa was an essential trigger for the activation of a Ca(2) (+) -activated Cl(-) -selective current. The dependence of PIC Ca(2) (+) signalling on 'T-type' and 'L-type' ICa is unique compared with other interstitial cells of the urogenital tract and may well be pharmaceutically exploitable.
Department of Physiology, School of Biomedical Sciences, Faculty of Medicine Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia.
Richard J
RJ
Lang
Mary A
MA
Tonta
Hiromichi
H
Takano
Hikaru
H
Hashitani
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000378:metabolism*; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D005071:Evoked Potentials / Q000187:drug effects; D006168:Guinea Pigs; D056885:Interstitial Cells of Cajal / Q000502:physiology*; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011467:Prostate / Q000166:cytology / Q000378:metabolism*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018118:Chloride Channels; D009543:Nifedipine
Ca2+-activated Cl- channels; L-type Ca2+ channels; T-type Ca2+ channels; calcium signalling; interstitial cells; prostate