Identification of a Hyperpolarization-activated Cyclic Nucleotide-gated Channel and Its Subtypes in the Urinary Bladder of the Rat

Objective To investigate the distribution and effects of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel and its isoforms in bladder, especially in bladder interstitial cells of Cajal (ICC). Methods Four HCN isoforms were detected in bladder tissue from rats using reverse transcription–polymerase chain reaction and Western blotting. The HCN1 subtype was observed in bladder ICCs by double-labeled fluorescence. The effect of the HCN blocker, ZD7288, was investigated using the bladder smooth muscle strip test. Results HCN1-4 isoforms were all identified in bladder ICCs using reverse transcription–polymerase chain reaction and Western blotting. Based on our semiquantitative analysis, HCN1 was found to be the most prominent isoform. The expression of HCN1 was confirmed in bladder ICCs by double-labeled fluorescence through colabeling of HCN1 and kit (CD117). ZD7288 significantly decreased the bladder excitation. Conclusion All 4 HCN channel isoforms exist in the bladder, and they affect the bladder excitation, presumably via bladder ICCs.