Previous work in the field has demonstrated two functionally distinct cell types in the rabbit urethra (Sergeant et aI, 2000) but it had never been adequately established that these cells could be clearly distinguished at a molecular level. In this study we demonstrate that urethral SMC and ICC differ at a molecular level. Using a wide range of molecular markers we have demonstrated that cells which were taken to be SMC, by their bright field appearance, did show expression of smooth muscle myosin and did not express any of the other markers. On the other hand, cells that were thought to be ICC expressed c-Kit and vimentin but did not express smooth muscle myosin. ICC exhibit rhythmic Ca2+ oscillations and it is believed that this activity underlies pacemaking in this tissue. Maintenance of this activity depends on influx of calcium through the plasma membrane and on activation of functional RyR and IP3 sensitive stores (Johnston et aI, 2005; Bradley et aI, 2006). We have identified RyR3 as being an essential component for the generation of Ca2+ waves. This statement is based on our finding that RyR3 is expressed in ICC, but is not expressed in SMC, which do not exhibit rhythmic oscillations. A third aim of the present study was to search for a molecular correlate of Ca2+ influx. From current research the most likely candidate appeared to be NCX and, interestingly, we were only able to detect the NCX3 isoform in urethral ICC. This conclusion is supported by the finding, in a recent study (Bradley et aI, 2006), that Ca2+ influx occurs via reverse mode NCX. We have demonstrated that HEK cells transfected so as to express RyR3, became rhythmically active which suggests that this RyR isoform is important in generating intracellular calcium oscillations. We demonstrated that these oscillations had an identical pharmacological profile to those observed in urethral ICC thus making HEK-RyR3 an ideal model for future work.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:491708 |
| Date | January 2008 |
| Creators | Large, Roddy Joseph |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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