thiourea and Urinary-Bladder--Overactive

The Na(+)/Ca(2+) exchanger (NCX) is thought to be a key molecule in the regulation of cytosolic Ca(2+) dynamics. The relative importance of the two Ca(2+) transport modes of NCX activity leading to Ca(2+) efflux (forward) and influx (reverse) in smooth muscle, however, remains unclear. Unexpectedly, spontaneous contractions of urinary bladder smooth muscle (UBSM) were enhanced in transgenic mice overexpressing NCX1.3 (NCX1.3(tg/tg)). The enhanced activity was attenuated by KB-R7943 or SN-6. Whole cell outward NCX current sensitive to KB-R7943 or Ni(2+) was readily detected in UBSM cells from NCX1.3(tg/tg) but not wild-type mice. Spontaneous Ca(2+) transients in myocytes of NCX1.3(tg/tg) were larger and frequently resulted in propagating events and global elevations in cytosolic Ca(2+) concentration. Significantly, NCX1.3(tg/tg) mice exhibited a pattern of more frequent urination of smaller volumes and this phenotype was reversed by oral administration of KB-R7943. On the other hand, KB-R7943 did not improve it in KB-R7943-insensitive (G833C-)NCX1.3(tg/tg) mice. We conclude that NCX1.3 overexpression is associated with abnormal urination owing to enhanced Ca(2+) influx via reverse mode NCX leading to prolonged, propagating spontaneous Ca(2+) release events and a potentiation of spontaneous UBSM contraction. These findings suggest the possibility that NCX is a candidate molecular target for overactive bladder therapy.

Topics: Animals; Anti-Arrhythmia Agents; Benzyl Compounds; Biological Transport, Active; Calcium; Male; Mice; Mice, Transgenic; Muscle Contraction; Muscle, Smooth; Sodium-Calcium Exchanger; Thiazolidines; Thiourea; Urinary Bladder; Urinary Bladder, Overactive

To investigate the effects of reactive oxygen species (ROS) on the micturition reflex in vivo, especially in bladder afferent signalling in rats, as several pathophysiological conditions in the urinary bladder (e.g. ischaemia/reperfusion and inflammation) are characterized by the formation of ROS.. Adult female Sprague-Dawley rats under urethane anaesthesia (normal or pretreated with 125 mg/kg capsaicin, subcutaneously, 4 days before) were assessed by continuous cystometrography (CMG) with or without the intravesical administration of H(2)O(2) (0.003-3%) to stimulate ROS damage. To investigate the mechanism of H(2)O(2), catalase (a H(2)O(2) scavenger) was applied intravesically (2000 IU/mL), or rats were given intravenous injections with superoxide dismutase (SOD, 20,000 IU/kg, a superoxide anion scavenger), dimethylthiourea (DMTU, 100 mg/kg, a hydroxyl radical scavenger), deferoxamine (20 mg/kg, an iron-chelator that prevents the formation of hydroxyl radical), indomethacin (3 mg/kg, a cyclooxygenase inhibitor) or ketoprofen (1 mg/kg, a cyclooxygenase inhibitor) just before or during the intravesical administration of H(2)O(2). Prostaglandin (PG) levels (PGE(2) and 6-keto-PGF(1 alpha)) were measured in the bladder of rats treated with intravesical 0.3% H(2)O(2) for 30 min with or without indomethacin.. Intravesical administration of H(2)O(2) induced detrusor overactivity, as shown by a reduction in the mean (sem) intercontraction interval (ICI), in a dose-dependent manner in normal rats (0.3% H(2)O(2,) P < 0.01, 36.2 (4.7)% of the control ICI). H(2)O(2)-induced detrusor overactivity was almost abolished by catalase and significantly suppressed by DMTU, deferoxamine, capsaicin pretreatment, indomethacin or ketoprofen but not by SOD. The level of PGs was significantly increased by H(2)O(2) instillation, and indomethacin significantly inhibited the increase in PGs.. These results indicate that oxidative stress induced by H(2)O(2) activates capsaicin-sensitive C-fibre afferent pathways, at least in part, mediated via stimulation of the cyclooxygenase pathway, thereby inducing detrusor overactivity. Thus, rats treated with intravesical H(2)O(2) appear to be a suitable model for the study of detrusor overactivity.

Topics: Afferent Pathways; Animals; Antioxidants; Capsaicin; Catalase; Cyclooxygenase Inhibitors; Deferoxamine; Dose-Response Relationship, Drug; Female; Free Radical Scavengers; Hydrogen Peroxide; Indomethacin; Ketoprofen; Prostaglandins; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Sensory System Agents; Siderophores; Superoxide Dismutase; Thiourea; Urinary Bladder; Urinary Bladder, Overactive; Urination