Gap junctions in der menschlichen Harnblase

Zusammenfassung

Fragestellung: Gap junctions sind Zellkontakte, welche im Sinne einer elektrischen Kopplung maßgeblich zur Synchronisation von Muskelzellaktionen beitragen. Da es noch immer umstritten ist, welche Bedeutung diese Interzellularverbindungen für die Funktion der Harnblasenmuskulatur besitzen, untersuchten wir das Vorkommen von Gap junctions und des Gap-junction-eigenen Strukturproteins Connexin (Cx) 45 im Detrusor der nicht obstruktiven stabilen Harnblase des Menschen. Material und Methode: Detrusorbiopsien von 6 Patienten im Alter von 64 (55 - 72) Jahren mit stabiler, nicht obstruktiver Harnblase wurden ultrastrukturell, molekularbiologisch und immunhistochemisch zum Nachweis von Gap junctions aufgearbeitet. Resultate: Transmissions- und Gefrierbruch-Elektronenmikroskopie zeigten Gap junctions an Zellmembranen von glatten Muskelzellen des Detrusors. Mittels Reverse Transcriptase (RT) Polymerase Chain Reaction (PCR) und In-situ-Hybridisierung fanden wir außerdem eine Expression von Cx45 im Detrusor. Dies wurde untermauert durch die Immunlokalisation von Cx45 an glatten Muskelzellen. Schlussfolgerung: Unsere Studie liefert morphologische sowie erstmals auch molekularbiologische und immunhistochemische Hinweise, dass die Muskelzellen der Harnblase durch Gap junctions elektrisch gekoppelt sind.

Abstract

Purpose: Gap junctions are intercellular contacts important for the synchronization of muscle cell activity through electrical coupling. Since the role of gap junctions for the function of smooth bladder muscle is still a matter of debate, we investigated the occurrence of gap junctions and the gap junctional protein connexin (Cx) 45 in the detrusor of the nonobstructed stable human bladder. Materials and methods: Detrusor biopsies from 6 patients aged 64 (55 - 72) years with stable nonobstructed bladders were investigated for the occurrence of gap junctions by electron microscopy, molecular biological techniques and immunohistochemistry. Results: Transmission electron microscopy and freeze fracture showed the presence of gap junction at plasma membranes of detrusor smooth muscle cells. By reverse transcriptase (RT) polymerase chain reaction (PCR) and in situ hybridization, we found an expression of Cx45 in the detrusor. These data were confirmed by immunolocalization of Cx45 on smooth muscle cells. Conclusions: This study provides morphological as well as molecular biological and immunohistochemical evidence that bladder smooth muscle cells are electrically coupled.

Schlüsselwörter

Gap junctions - Harnblase - Miktion - Connexin 45

Key words

Gap junctions - bladder - micturition - connexin 45

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