The effects of exogenous prostaglandins and the identification of constitutive cyclooxygenase I and II immunoreactivity in the normal guinea pig bladder

Abstract

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 of Cajal in the Urinary Tract

“…The ICC-LP network is closely associated with mucosal nerves as shown by confocal imaging where Kit-positive cells made contacts with anti-PGP9.5 labeled nerves (Davidson and McCloskey 2005) and by TEM which demonstrated close contacts between ICC-LP and nerve endings (Wiseman et al 2003). Recent work has shown that human bladder ICC-LP make frequent structural associations with a mucosal cholinergic plexus (Johnston et al 2008;submitted), consistent with the finding that ICC-LP express M2 and M3 muscarinic receptors (Mukerji et al 2006;Grol et al 2009). de Jongh et al (2007 suggested that cells resembling lCC-LP were immunopositive for cyclooxygenase 1; furthermore, Ost et al (2002) reported vanilloid receptor immunoreactivity giving further insight into the pharmacological profile of these cells.…”

“…The cholinergic signaling pathway in these cells has been shown to be mediated largely via M 3 muscarinic receptors and an IP 3 and ryanodine receptor-dependent release of Ca ) and this difference may represent an important division of labor between two ICC subtypes in the bladder. The physiological consequence of the detrusor ICCs' Ca 2+ -response to cholinergic stimulation has not yet been ascertained, although Johnston et al (2008) suggested that release of transmitter substances may result, consistent with the observation of vesicles in ICC from TEM studies (Rasmussen et al 2009;Cunningham et al 2009). de Jongh et al (2007 suggested that ICC may release prostaglandins and further work is necessary to determine whether detrusor ICC actually exhibit a secretory-type function.…”

Hydrogen Sulfide Plays a Key Role in the Inhibitory Neurotransmission to the Pig Intravesical Ureter

“…The COX pathway is involved in bladder physiology and pathology, and several studies have demonstrated a role for COX-derived prostanoids in the neural control of bladder smooth muscle tone [11],[29],[30],[31]. In the current study, indomethacin, a COX inhibitor, failed to modify the EFS or GYY4137 relaxations, thus indicating that COX-derived prostanoids are not likely to be involved in the H 2 S responses.…”

Mechanisms involved in the nitric oxide independent inhibitory neurotransmission to the pig urinary bladder neck

“…11 During the filling phase, the urinary bladder shows local contractions and relaxations produced by a basal myogenic mechanical activity that may be increased by the local release of prostaglandins. These spontaneous contractions are able to generate activity in afferent nerves, that may contribute to detrusor overactivity.…”