Voltage-operated Ca(2) (+) currents and Ca(2) (+) -activated Cl(-) currents in single interstitial cells of the...

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

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

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.

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.