OBJECTIVES To establish the functional consequences of exposing the isolated whole bladder preparation to exogenous prostaglandins (PGE1, PGE2, PGF2α) and to determine which cells express cyclooxygenase (COX) types I and II, to generate PG to effect these changes in vivo. MATERIALS AND METHODS Fifteen female guinea pigs (270–350 g) were used, i.e. seven for structural studies and eight for physiological measurement. For the structural study pieces of the lateral wall were incubated separately in Krebs’ solution at 36 °C, gassed with 95% O2 and 5% CO2 with 1 mm isobutyl‐methyl‐xanthene. Individual pieces were then exposed to 100 µm of the nitric oxide (NO) donor NONOate for 10 min; control tissues remained in Krebs’ solution. Tissues were then fixed in 4% paraformaldehyde. For the physiological experiments bladders were isolated and a cannula inserted into the urethra to monitor intravesical pressure. The bladders were suspended in a chamber containing carboxygenated physiological solution at 33–36 °C. All drugs were added to the abluminal bladder surface. RESULTS In the resting bladder there were small spontaneous transient rises in pressure, i.e. autonomous activity. Exposure to PGE2 (3–300 nm) resulted in an increase in basal pressure on which were superimposed autonomous activity, which was increased both in amplitude and frequency. The changes in the amplitude and frequency depended on the concentration of PGE2. After a brief exposure (240 s) to PGE2 the augmentation of the autonomous activity continued for >60 min despite regular washing. The responses were similar with PGE1 but the responses to PGF2α and arachidonic acid were reduced. The augmented activity was reduced by the EP1/EP2 receptor blocking agent AH6809 (10 µm). Using an antibody to the 70 kDa constitutive form (COX I), COX I immunoreactivity (COX I‐IR) was located in cells in the basal urothelium, in lamina propria and cells on the surface of the inner muscle bundles. There were few COX I‐IR cells associated with the outer muscle bundles. The COX I‐IR cells lying within the lamina propria were distinct from the suburothelial cells which respond to NO with an increase in cGMP. The lamina propria COX I‐IR cells appeared to form a network surrounding muscle trabeculae within the inner muscle layer. COX II‐IR was associated with the nuclei of cells in the urothelium, lamina propria and muscle. CONCLUSIONS These data show that PGs regulate autonomous activity. Potential sources of endogenous PG were identified. It is unclear how the PGs produced by these cells alter autonomous activity. There might be a direct activation of the muscle by PGs released by the network of superficial muscle interstitial cells, or PG released from the urothelium might influence phasic contractile activity via networks of COX I‐IR interstitial cells. The possible roles and importance of this mechanism for bladder physiology and pathology are discussed.

Interstitial cells (ICs) play a role in regulating normal bladder activity. This study explores the possibility that the sub-urothelial and muscle networks of NO/cGMP-responsive ICs are altered in animals with surgically induced outflow obstruction. In sham-operated animals, the urothelium comprised NO-stimulated cGMP-positive (cGMP(+)) umbrella cells, an intermediate layer and a basal layer that stained for nNOS. cGMP(+) sub-urothelial interstitial cells (su-ICs) were found below the urothelium. cGMP(+) cells were also associated with the outer muscle layers: on the serosal surface, on the surface of the muscle bundles and within the muscle bundles. Several differences were noted in tissues from obstructed animals: (1) the number of cGMP(+) umbrella cells and intensity of staining was reduced; (2) the intermediate layer of the urothelium consisted of multiple cell layers; (3) the su-IC layer was increased, with cells dispersed being throughout the lamina propria; (4) cGMP(+) cells were found within the inner muscle layer forming nodes between the muscle bundles; (5) the number of cells forming the muscle coat (serosa) was increased; (6) an extensive network of cGMP(+) cells penetrated the muscle bundles; (7) cGMP(+) cells surrounded the muscle bundles and nodes of ICs were apparent, these nodes being associated with nerve fibres; (8) nerves were found in the lamina propria but rarely associated with the urothelium. Thus, changes occur in the networks of ICs following bladder outflow obstruction. These changes must have functional consequences, some of which are discussed.

Localized phasic contractions in the bladder wall (autonomous activity) have been hypothesized to be an integral part of a motor/sensory system contributing to bladder sensation. The sites responsible for generating this activity, the mechanisms involved in its propagation and modulation remain unknown. This phasic motor activity is modulated by exogenous prostaglandins. Therefore, analysis of the sites of prostaglandin production and action within the bladder wall may shed light on the mechanisms of generation and modulation of this phasic activity. In this paper we report the localization of immuno-reactivity indicative of the expression of cyclo-oxygenase enzyme type I (COX I-IR) within the bladder wall. Basically, three types of COX I-IR cell were identified: epithelial cells in the basal and intermediate layers of the urothelium, complex vimentin-positive and COX I-IR cells in the lamina propria and vimentin-negative COX I-IR cells in the lamina propria and on the surface of the inner muscle bundles. These vimentin-negative/COX I-IR cells appear to be in close apposition to a continuous network of vimentin-positive cells, which extends from the lamina propria into the inner muscle layers and subsequently into the outer muscle layers. However, the interstitial cells in this region might form a distinctly different sub-type. First, the interstitial cells in this region differ from those in the inner layer by their responsiveness to NO with a rise in cGMP. Two subtypes have been identified: cells on the surface of the muscle bundles and within the muscle bundles. Second, COX I-IR cells are not associated with the interstitial cells in the outer layers. The physiological significance for these apparent differences in the interstitial cell network is not clear. However, such differences are likely to reflect differences in the processes involved in their activation, modulation and control.

The results of our study demonstrate that oxidative stress induced by CHP affects pig bladder contractility. The muscarinic receptor signaling system is severely damaged. L-type calcium channels and the contractile system are less affected and cholinergic nerves remain largely unaffected.