AB283. SPR-10 Down-regulation of ryanodine receptor gene expression in murine urinary bladder smooth muscle following partial bladder outlet obstruction

Objective: Urinary bladder smooth muscle (UBSM) displays spontaneous action potentials and this potential is related to the phasic nature of spontaneous contractions in this tissue. The amplitude of a phasic contraction depends on the increase in Ca²⁺ entry caused by membrane depolarization. Ryanodine receptors (RyRs) in UBSM decreases the force production by decreasing the frequency of phasic contractions through interactions with large-conductance Ca²⁺-activated K⁺ (BK) and small-conductance Ca²⁺-activated K⁺ (SK) channels. Microarray and network analysis were employed to determine the changes in mRNA in 14-day obstructed murine bladders. We found that obstruction significantly down-regulated the RyRs in bladder smooth muscle (BSM).

Methods: Male C57Bl/6 mice were surgically obstructed and kept for 14 days. Sham-operated mice served as a control. Bladders were excised; urothelium scraped off with a scalpel, and the serosa was removed. BSM obtained from PBOO and sham control animals were used for microarray and western blotting

Results: Pathway-based analysis of these gene signatures showed significant number of under-expressed genes in obstructed bladder and they were mapped to proteins involved in calcium signaling. We focused our work on RyR protein expression in BSM. There was a four-fold reduction of RyR3 in BSM in 14-day obstructed groups as shown by microarray and immunoblotting compared to that of sham-operated animals.

Conclusions: These results confirm that the RyR gene expression is down-regulated in obstructed murine bladder smooth muscle.

Funding Source(s): None

Keywords: Bladder; outlet obstruction; ryanodine receptor (RyR); gene expression; western blot