Gesteigerte Expression des Tunnelproteins Connexin43 in der obstruierten Rattenblase - eine mögliche Ursache obstruktionsbedingter Blasenhyperaktivität

Zusammenfassung

Fragestellung: Blasenhyperaktivität ist ein häufiges und belastendes Symptom der Blasenauslassobstruktion und persistiert oft auch nach effektiver Deobstruierung. Gap junctions werden schon länger als mögliche Ursache von Blasenhyperaktivität diskutiert. Wir untersuchten die regionale Verteilung des Gap-junction-Proteins Connexin43 in obstruierten und nicht obstruierten Rattenblasen. Material und Methode: Durch partielle Ligatur der Urethra wurde eine Obstruktion bei weiblichen Ratten erzeugt. Nach 6 Wochen wurden die Blasen entnommen und für den molekularbiologischen Nachweis von Connexin43-mRNS durch kompetitive RT-PCR oder die immunhistochemische Detektion von Connexin43-Protein weiterverarbeitet. Ergebnisse: Connexin43-mRNS war in allen Detrusorproben nachweisbar, in den obstruierten Gewebsproben überstieg die mRNS-Konzentration die der normalen Rattenblasen um mindestens das Zweifache. Eine Connexin43-Immunfluoreszenz konnte bei normalen Detrusorproben nicht nachgewiesen werden, jedoch zeigten alle obstruierten Präparate eine immunhistochemische Reaktion. Schlussfolgerung: Die Ergebnisse unterstützen die Hypothese, dass die infolge der Auslassobstruktion hypertrophierten Blasen-Leiomyozyten einen erniedrigten elektrischen Widerstand aufweisen und zur Aufrechterhaltung einer adäquaten interzellulären Signaltransduktion kompensatorisch eine gesteigerte Gap junction-Expression induzieren. Dadurch könnten Gap junctions über eine intensivere Zellverkoppelung eine Blaseninstabilität mitverursachen.

Abstract

Purpose: Bladder hyperactivity is a frequent and embarassing symptom of bladder outlet obstruction and often persists even after effective removal of the obstruction. It has been proposed that gap junctions be present in models of bladder overactivity including outlet obstruction. We therefore determined whether the gap junction protein connexin43 and its associated mRNA were present in normal and obstructed rat bladders. Materials and Methods: Obstruction was created in female Sprague-Dawley rats by placement of a ligature around the urethra which limited urethral opening; the ligature was omitted in controls. After 6 weeks, bladders were harvested and processed for detection of connexin43 mRNA by competitive RT-PCR or connexin43 protein by immunohistochemistry. Results: Connexin43 mRNA was present in control bladders and at least 2-fold upregulated in obstructed bladders. No connexin43 immunoreactivity was observed in control bladder smooth muscle. Connexin43 immunoreactivity between bladder smooth muscle cells was present in all obstructed bladders and presumably represents gap junctions. Conclusions: The results directly support the hypothesis that gap junctions are upregulated in obstructed bladders due to lowered input resistance of hypertrophied myocytes. Thus, they may contribute to bladder instability by increasing intercellular electrical coupling.

Blase - Connexine - “Gap junctions” - Immunhistochemie - RT-PCR

bladder - connexins - gap junctions - immunohistochemistry - RT-PCR

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