Identification of T-type calcium channels in the interstitial cells of Cajal in rat bladder

Objective: To investigate the expression and function of T-type calcium channels in the interstitial cells of Cajal in rat bladders.

Methods: Bladders were harvested from Sprague-Dawley rats. The expression of T-type calcium channels subtypes (α1G, α1H, and α1I) in interstitial cells of Cajal were identified by double-labeled immunofluorescence analysis and reverse transcription-polymerase chain reaction analysis in whole mount preparations of rat bladders. The function of T-type calcium channels in freshly isolated interstitial cells of Cajal was assessed by detecting the changes of intracellular calcium ([Ca(2+)](i)) with preloading fluo-3 AM, and by evaluating the changes of the phasic contractions of rat bladder strips after treating with mibefradil and glivec.

Results: Three T-type calcium channels subtypes, α1G, α1H, and α1I, colocalized with c-kit in bladder interstitial cells of Cajal by double-labeled immunofluorescence analysis, and this was confirmed using reverse transcription-polymerase chain reaction. The T-type calcium channels selective blocker, mibefradil (1 μM), significantly decreased the intracellular calcium concentration ([Ca(2+)](i)) in isolated interstitial cells of Cajal (P < .01) and inhibited the spontaneous phasic contraction of bladder strips (P < .01). Moreover, the c-kit receptor blocker, glivec, significantly decreased the [Ca(2+)](i) of interstitial cells of Cajal further (P < .01) and the spontaneous phasic contraction of bladder strips.

Conclusion: T-type calcium channel subtypes were confirmed to colocalize in interstitial cells of Cajal in rats bladders, which might participate in the spontaneous activity of interstitial cells of Cajal and phasic contractions of bladder strips by modulating [Ca(2+)](i) in interstitial cells of Cajal.