Pacemaker activity in urethral interstitial cells is not dependent on capacitative calcium entry

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Abstract
The aim of the present study was to investigate the properties and role of capacitative Ca2+entry (CCE) in interstitial cells (IC) isolated from the rabbit urethra. Ca2+entry in IC was larger in cells with depleted intracellular Ca2+stores compared with controls, consistent with influx via a CCE pathway. The nonselective Ca2+entry blockers Gd3+(10 μM), La3+(10 μM), and Ni2+(100 μM) reduced CCE by 67% ( n = 14), 65% ( n = 11), and 55% ( n = 9), respectively. These agents did not inhibit Ca2+entry when stores were not depleted. Conversely, CCE in IC was resistant to SKF-96365 (10 μM), wortmannin (10 μM), and nifedipine (1 μM). Spontaneous transient inward currents were recorded from IC voltage-clamped at −60 mV. These events were not significantly affected by Gd3+(10 μM) or La3+(10 μM) and were only slightly decreased in amplitude by 100 μM Ni2+. The results from this study demonstrate that freshly dispersed IC from the rabbit urethra possess a CCE pathway. However, influx via this pathway does not appear to contribute to spontaneous activity in these cells.