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 Ca entry caused by membrane depolarization. Ryanodine receptors (RyRs) in UBSM decreases the force production by decreasing the frequency of phasic contractions through interactions with largeconductance Ca-activated K (BK) and small-conductance Ca-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 shamoperated animals. Conclusions: These results confirm that the RyR gene expression is down-regulated in obstructed murine bladder smooth muscle. Funding Source(s): None