Figure 9.

K_ATP is expressed in umbrella cells and modulates the stretch response. (A) Expression of the indicated K⁺ channels was detected by RT-PCR of total RNA isolated from mouse bladder uroepithelium. Numbers above the DNA species are the expected product sizes of the RT-PCR reaction (in base pairs). (B) A lysate of rat uroepithelium was resolved by SDS-PAGE and a Western blot probed with antibody specific for the Kir6.1 subunit of K_ATP. The nominal mass of the major protein detected in the lysate is indicated to the right of the panel. (C) Frozen thin sections of rat bladder tissue were labeled with an antibody to the Kir6.1 subunit of K_ATP (green), claudin-4 (red) to label the basolateral membranes of the umbrella cells and plasma membranes of the underling intermediate and basal cells and Topro-3 to label the cell nuclei (blue). A merged panel is shown at the right. Bar, 10 μm. (D) The indicated K⁺ channel openers were added to the serosal hemichamber and incubated with tissue for 30 min. The tissue was then bowed outward by filling the chamber with a 20-gauge needle at a 2 cm H₂O pressure head. The experiments were repeated ≥3 times, and representative results are shown.