[Evidence of occurrence of gap junctions in stable nonobstructed human bladder]

To investigate the occurrence of gap junctions and the gap junction forming protein connexin (Cx) in normal human detrusor.

Specimens of detrusor smooth muscle were obtained from 6 patients with localized bladder tumors during radical cystectomy. Transmission electron microscopy and freeze fracture microscopy were used to observe the microstructure of the detrusor smooth muscle. Reverse transcription polymerase chain reaction (RT-PCR) and fluorescence immunohistochemistry was used to detect the expression of Cx in the detrusor smooth muscle.

Ultrastructural and freeze fracture studies showed gap junctions in the detrusor smooth muscle cells. However, these gap junctions appeared to be small and irregularly shaped. RT-PCR amplified 2 fragments with the lengths of 300 bp and 200 bp, and sequencing showed that they were identical with the Cx45 already published. Fluorescence immunohistochemistry showed the existence of immunological signal of Cx45 in most of the detrusor smooth muscles.

The smooth muscle cells of stable human detrusor are electrically coupled through gap junctions.