The influence of vesical distension on the urethral resistance to flow: a possible role for prostaglandins?

Urothelial mucosal signaling and the overactive bladder-ICI-RS 2013

There is abundant evidence that the lower urinary tract (LUT) mucosal layer is involved both in mechanosensory functions that regulate bladder contractile activity and in urethral sensation. Changes to the mucosa can be associated with a number of bladder pathologies. For example, alterations of the urothelium and underlying lamina propria at both the molecular and structural levels have been reported in both patients and animals associated with disorders such as bladder pain syndrome and diabetic cystopathy. In contrast to the urinary bladder, much less is known about the urothelium/lamina propria of the bladder neck/proximal urethra. There are important gender differences in the outflow region both anatomically and with respect to innervation, hormonal sensitivity, and location of the external urethral sphincter. There is reasonable evidence to support the view that the mucosal signaling pathway in the proximal urethra is important for normal voiding, but it has also been speculated that the proximal urethra can initiate bladder overactivity. When dysfunctional, the proximal urethra may be an interesting target, for example, botulinum toxin injections aiming at eliminating both urgency and incontinence due to detrusor overactivity.

Purinergic signalling in the urinary tract in health and disease

Purinergic signalling is involved in a number of physiological and pathophysiological activities in the lower urinary tract. In the bladder of laboratory animals there is parasympathetic excitatory cotransmission with the purinergic and cholinergic components being approximately equal, acting via P2X1 and muscarinic receptors, respectively. Purinergic mechanosensory transduction occurs where ATP, released from urothelial cells during distension of bladder and ureter, acts on P2X3 and P2X2/3 receptors on suburothelial sensory nerves to initiate the voiding reflex, via low threshold fibres, and nociception, via high threshold fibres. In human bladder the purinergic component of parasympathetic cotransmission is less than 3 %, but in pathological conditions, such as interstitial cystitis, obstructed and neuropathic bladder, the purinergic component is increased to 40 %. Other pathological conditions of the bladder have been shown to involve purinoceptor-mediated activities, including multiple sclerosis, ischaemia, diabetes, cancer and bacterial infections. In the ureter, P2X7 receptors have been implicated in inflammation and fibrosis. Purinergic therapeutic strategies are being explored that hopefully will be developed and bring benefit and relief to many patients with urinary tract disorders.

Prostaglandin E2-induced bladder hyperactivity in normal, conscious rats: involvement of tachykinins?

In normal conscious rats investigated by continuous cystometry, intravesically instilled prostaglandin (PG) E2 facilitated micturition and increased basal intravesical pressure. The effect was attenuated by both the NK1 receptor selective antagonist RP 67,580 and the NK2 receptor selective antagonist SR 48,968, given intra-arterially, suggesting that it was mediated by stimulation of both NK1 and NK2 receptors. Intra-arterially given PGE2 produced a distinct increase in bladder pressure before initiating a micturition reflex, indicating that the PG had a direct contractant effect on the detrusor smooth muscle. The effect of intra-arterial PGE2 could not be blocked by intra-arterial RP 67,580 or SR 48,968, which opens the possibility that the micturition reflex elicited by intra-arterial PGE2 was mediated by pathways other than the reflex initiated when the PG was given intravesically. The present results thus suggest that intra-arterial PGE2, given near the bladder, may initiate micturition in the normal rat chiefly by directly contracting the smooth muscle of the detrusor. However, when given intravesically, PGE2 may stimulate micturition by releasing tachykinins from nerves in and/or immediately below the urothelium. These tachykinins, in turn, initiate a micturition reflex by stimulating NK1 and NK2 receptors. Prostanoids may, via release of tachykinins, contribute to both urge and bladder hyperactivity seen in inflammatory conditions of the lower urinary tract.

Effects of distension of the urinary bladder on the cardiovascular reflexes from the carotid baroreceptors in the dog

1. The hindlimb vasoconstrictor effects of distension of the urinary bladder were studied at different levels of input from the carotid sinus baroreceptors in the dog anaesthetized with a mixture of chloralose and urethane. 2. The vascularly isolated hindlimb was perfused at constant blood flow through its femoral artery, so that a change in pressure gradient (mean femoral arterial perfusion pressure minus mean inferior vena caval pressure) indicated a similar directional change in vascular resistance. The vascularly isolated carotid sinus regions were perfused with blood at a constant pulsatile flow. 3. Raising the carotid sinus mean perfusion pressure in randomly selected steps of 30 mmHg from 60 to 210 mmHg had little effect on heart rate unless the blood pressure was controlled, when a progressive bradycardia occurred, but caused a progressive reduction in arterial blood pressure and vasodilatation in the perfused hindlimb. Distension of the bladder at each level of carotid sinus pressure resulted in tachycardia, hypertension and hindlimb vasoconstriction. 4. The cardiac responses to bladder distension were the same at all carotid sinus pressures. When the blood pressure was controlled, however, the response was reduced at high and low sinus pressures. 5. The relationship between the carotid sinus perfusion pressure and hindlimb perfusion pressure (i.e. vascular resistance) was affected by distension of the bladder in two ways. In the one, hindlimb perfusion pressure increased by approximately the same amount at all levels of carotid sinus pressure indicating resetting of the carotid sinus baroreceptor reflex control of hindlimb vascular resistance towards vasoconstriction without change in gain of the reflex. In the other, the pressure increases were diminished at the higher levels of carotid sinus pressure indicating both resetting and an increase in gain of the reflex. 6. Both types of response occurred in the spontaneously breathing animal, in animals artificially ventilated, while pacing the heart, with the arterial blood pressure maintained constant at about 100 mmHg, and after division of the cervical vagosympathetic nerves. The frequency of occurrence of each type of response, however, varied under the different conditions. 7. The possible reasons for the two types of vascular response are discussed.

Indomethacin suppository to treat primary nocturnal enuresis: double-blind study

The prostaglandin synthesis inhibitor indomethacin (used as a suppository) was compared to placebo in the treatment of primary nocturnal enuresis in a double-blind crossover study. There were 12 girls and 7 boys between 6 and 15 years old. Indomethacin (50 to 100 mg.) was significantly more effective than placebo in the treatment of primary enuresis.

The effect of SC-19220, a prostaglandin antagonist, on the micturition reflex in rats

SC-19220 (5-20 mg/kg i.v.), a competitive receptor antagonist of PGE, increased the bladder capacity and reduced the voiding efficiency of micturition (elicited by slow transvesical filling) of urethane-anesthetized rats. The effect of SC-19220 was prevented by indomethacin pretreatment, whereas indomethacin per se mimicked the effects of SC-19220. SC-19220 produced a competitive rightward shift of the dose-response curve for the contractile effect induced by PGE2 on strips of rat detrusor muscle in vitro, whereas the amplitude of nerve-mediated twitches was unaffected. These findings support the hypothesis that endogenous PGE2 is physiologically involved in the regulation of vesicourethral motility in this species by facilitating attainment of the micturition threshold during the collection phase of the cystometrogram.

Regulation of prostaglandin synthesis by reduced glutathione in urinary bladder epithelium

A possible mechanism is presented by which reduced glutathione (GSH) regulates prostaglandin (PG) synthesis in microsomes of the porcine bladder epithelium. At a concentration of GSH less than 10(-5) M, microsomes produced more PGI2 and PGF2 alpha than PGE2. At a greater GSH concentration, PGE2 synthesis was remarkably enhanced. On the other hand, PGI2 and PGF2 alpha synthesis was inhibited. In the presence of 10(-3) M GSH, ten times more PGE2 was produced than the other PGs. The concentration of GSH in porcine bladder epithelium was about 0.6 mM. This reciprocal effect of GSH was also observed in rabbit and bovine bladder epithelium. These findings suggest that GSH is involved in the regulation of PG synthesis in urinary bladder epithelium. GSH may influence the physiological and pathophysiological changes elicited by PGs in the lower urinary tract.

Prostanoids modulate reflex micturition by acting through capsaicin-sensitive afferents

Topical application of exogenous prostanoids (PGE2, TBX B2) on the serosal surface of the urinary bladder of urethane-anaesthetized rats activated reflex micturition. Likewise, intravesical instillation of PGE2 during the cystometrogram lowered the threshold for reflex micturition. Both effects were prevented by systemic capsaicin desensitization (50 mg/kg s.c., 4 days before). Indomethacin pretreatment and systemic capsaicin desensitization each increased the micturition threshold without affecting the amplitude of micturition contraction. However, the effect of the two treatments combined was not greater than the effect of either alone. These findings support the idea that endogenous prostanoids facilitate reflex micturition by stimulating or sensitizing, directly or indirectly, the subset of bladder mechanoreceptors which is capsaicin-sensitive in adult rats.

Influence of prostaglandins and ketoprofen on contractile responses of human and pig detrusor and trigone muscles in vitro

Detrusor and trigone smooth muscle from pig and man were investigated in vitro. The strips were adjusted to a tension of 1 g. During the first hour detrusor strips relaxed and had to be lengthened repeatedly to maintain tension. The tension of strips from the trigone increased spontaneously during this initial period of recovery and accommodation. Detrusor contractions evoked by transmural electric field stimulation, carbachol, histamine and Ca++ were reduced by ketoprofen (an inhibitor of prostaglandin synthesis), while contractions evoked in trigone strips were augmented by ketoprofen. PGE2 10 nM reversed the effect of prostaglandin synthesis antagonism, augmenting the reduced detrusor response and reducing the augmented trigone response. PGF2 alpha augmented evoked contractions in strips from all regions. Activation of endogenous prostaglandin production can not explain the strip behavior during recovery. After recovery, synthesis of the E-type of prostaglandins seem to dominate over the F-type of prostaglandins, since annulment of the E-type of prostaglandins explains best the alterations of evoked contractions following prostaglandin synthesis antagonism.

Diclofenac sodium in the treatment of primary nocturnal enuresis: double-blind crossover study

The prostaglandin synthesis inhibitor diclofenac sodium has been compared with a placebo in the treatment of primary nocturnal enuresis in a double-blind crossover trial. Twenty patients were entered: 14 female, six male; age range 6-17 years. The results showed that diclofenac sodium was significantly more effective than placebo in the treatment of nocturnal enuresis.

Changes in vascular resistance in the feline urinary bladder in response to bladder filling

The effect of bladder filling on vesical blood flow was studied in anesthetized cats. The pelvic nerves were sectioned and the bladder venous outflow was recorded by a drop counter. Filling of the bladder induced a sustained increase in vesical blood flow, related to the bladder volume. Thus, injection of 10, 20 and 30 ml. of saline decreased bladder vascular resistance by 27, 47 and 52 per cent, respectively. This vasodilation occurred despite a steady state increase in bladder pressure by 25 to 50 cm. H2O. Upon emptying of the bladder, blood flow decreased towards control values. The response was unaffected by alpha-adrenoceptor blockade (phentolamine), beta-adrenoceptor blockade (propranolol) and muscarinic cholinoceptor blockade (atropine). The vasodilation was eliminated by papaverine, indicating that the response was not due to a rearrangement of the vessels at large bladder volumes. The vasodilation was not associated with any increase in the concentrations of vasoactive intestinal polypeptide (VIP) or substance P in the venous effluent blood. Indomethacin significantly reduced the vasodilatation induced by filling. We conclude that local mechanisms, possibly involving release of prostaglandins, are involved in the vasodilation following bladder distension.

The effect of cyclooxygenase inhibitors on the low filling rate cystometrogram in urethane anesthetized rats

The effect of two widely used cyclooxygenase inhibitors (indomethacin and ketoprofen) on the low filling rate cystometrogram was investigated in urethane anesthetized rats. Both indomethacin and ketoprofen significantly increased volume threshold to elicit neurogenic bladder contractions without affecting their amplitude. Also the pressure threshold was unaffected by both drugs while the volume/pressure relationship was significantly flattened compared to controls. These findings indicate that acute suppression of arachidonic acid metabolism along the cyclooxygenase pathway increases the micturition threshold without affecting bladder muscle contractility and/or neurotransmission along the efferent pathway of the micturition reflex.

Release of arachidonate cascade products by the rabbit bladder; neurophysiological significance?

The endogenous production of prostaglandins and thromboxane A2 by the rabbit urinary bladder was assessed by radioimmunoassay in a relatively intact system and in the absence of substrate. PGE2 and PGI2 (prostacyclin) were the main prostaglandins released whereas PGF2 alpha ratio of 5:1 and a PGI2 to PGF2 alpha ratio of 3:1 were observed. This qualitative pattern was independent of bladder area. In addition, prostaglandin release by the bladder body was significantly greater than by the bladder base at all incubation times. The physiological implications of these experimental observations are discussed.

Response of urethral smooth muscles to pharmacological agents. II. Noncholinergic, nonadrenergic agonists and antagonists

We studied the effects of a variety of noncholinergic, nonadrenergic agents on the smooth muscles of the cat urethra. Prostaglandin F2 alpha contracted both urethral muscle layers to a similar extent. Prostaglandin E2 contracted the longitudinal and relaxed the circular muscle layers. The effects of the prostaglandins seem to be directly myogenic since cholinergic and adrenergic blockers and tetrodotoxin did not affect them. Bradykinin and substance P contracted both urethral muscle layers. Other tested agonists (neurotensin, vasoactive intestinal peptide, cyclic 3,5 adenosine monophosphate, adenosine diphosphate sodium, cyclic 3,5 guanosine monophosphate sodium, bombesin) had no effect on the cat urethral smooth muscles.

Pharmacological analysis of the responses of the feline urethra to autonomic nerve stimulation

The effects of sympathetic and parasympathetic nerve stimulation on resistance to flow in the proximal urethra was examined in male, chloralose-anesthetized cats. Hypogastric (sympathetic) nerve stimulation increased urethral resistance, an effect that was blocked by the alpha-adrenergic antagonist prazosin (0.1 mg/kg), reduced 50% by ganglionic blockade with hexamethonium (0.4 to 0.6 mg/min) and potentiated by the beta-adrenergic antagonist sotalol (5 mg/kg). In the presence of phenylephrine-induced constrictions of the urethra, hypogastric nerve stimulation decreased resistance by a sotalol-sensitive, hexamethonium-resistant mechanism. The results imply that sympathetic stimulation can either raise or lower urethral resistance under different conditions, and that the organization of the nerves mediating the two types of response differs. Because pelvic nerve stimulation produced small and inconsistent responses, the parasympathetic input was instead activated by sacral ventral root stimulation. Sacral stimulation produced an atropine-sensitive constriction when basal urethral resistance was low, and dilatation when resistance was high. The latter response was reduced by atropine, but was resistant to sotalol. However, the decrease in resistance produced by acetylcholine in the presence of PE was not reduced by atropine, implying that acetylcholine-induced dilatation of the urethra is not due to activation of muscarinic receptors on smooth muscle. It is hypothesized that parasympathetic dilatation of the urethra may be mediated by a non-cholinergic, non-adrenergic inhibitory transmitter released from post-ganglionic neurons. A muscarinic mechanism may be involved in this response either to potentiate the action of the unknown transmitter or to facilitate the ganglionic excitation of these neurons. Parasympathetic constrictor responses can be attributed to activation of postganglionic cholinergic neurons.

Prostaglandin type E activity dominates in urinary tract smooth muscle in vitro

Changes in isometric tension and spontaneous contractions in human and porcine lower urinary tract smooth muscle strips caused by PGE2, PGF2a and the prostaglandin biosynthesis inhibitor ketoprofen were investigated in vitro. Ketoprofen reduced the prostaglandin biosynthesis significantly and caused reversible and dose dependent decreases of tension and spontaneous contractions in detrusor strips, while tension increase was induced in strips from the urethra, bladder neck and trigone. PGE2 reestablished the tension and the spontaneous activity in the detrusor strips and counteracted the tension increase in strips from the urethra, bladder neck and trigone. PGF2a increased the tension in all strips. The threshold concentration for prostaglandin effect in strips pretreated with ketoprofen was 10(-10) - 10(-9) mol./l., a concentration which might be considered physiologically relevant. Prostaglandin synthesis inhibition thus caused responses opposite to those of PGE2 in every single strip. These results strongly suggest the PGE-type of activity to be more important than the PGF-type of activity in lower urinary tract smooth muscle in vitro.

Non-cholinergic, non-adrenergic nerve mediated relaxation of trigone, bladder neck and urethral smooth muscle in vitro

Human trigone and porcine urethral, bladder neck and trigone smooth muscle were exposed to transmural electric field stimulation in vitro. The responses were composed of different combinations of a relaxation phase and a contraction phase. A few strips exhibited contractions only and a few strips relaxation only. The individual strip retained the behavior throughout the experiment. No systematic difference in the responses was found in strips from the different regions. The configuration of the response was slightly shifted in favor of contraction by beta-adrenergic blockade with propanolol and prostaglandin synthesis inhibition with Ketoprofen. After alpha-adrenergic blockade with phentolamine and cholinergic blockade with atropine, the reverse effect was seen with augmentation of the relaxation and reduction of the contraction. The relaxation phase was completely abolished by nerve poisoning with tetrodotoxin, but was still observed with all other antagonists present, and was therefore nerve-mediated through non-cholinergic, non-adrenergic and non-prostaglandin transmitter or modulator systems.

Effect of prostaglandin on urethral resistance and micturition

The effect of four exogenous prostaglandins, PGA1, PG802, PGE2 and PGF2 alpha, upon the lower urinary tract was investigated in female mongrel dogs without neurogenic lesions in vivo. The urethral resistance was studied by means of a urethral pressure profile, and the bladder function by evaluating whether or not the micturition was triggered. The reduction of urethral resistance in terms of the maximum urethral closure pressure was most significant with PGE2 given intraaterially. Micturition was most frequently provoked by the intravenous administration of PG802, a derivative of PGE1. PGE series seemed to be the most potent for the evacuation of urine in female dogs.

The effect of exogenous prostaglandins F2 alpha and E2 and indomethacin on micturition

The influence of exogeneous infusion of prostaglandins (PGs) of the F2 alpha and E2 series and of indomethacin on micturition cycles was investigated in 30 anaesthetised female dogs. In 30 other animals, urethrovesical disconnection was performed to study the action of PGs and of indomethacin without the muscle continuity factors. In the intact animal model during vesical distension, PGE2 produced a significant urethral pressure drop and a dose-dependent reduction in the threshold micturition volume. PGF2 alpha produced a significant urethral pressure rise. At doses higher than 0.3 micrograms/kg, PGF2 alpha reduced the threshold micturition volume. On the other hand, indomethacin significantly increased the threshold micturition volume and reduced the maximum intravesical pressure. In the disconnected model, PGE2 produced a dose-dependent decrease in the resting urethral pressure and hardly affected the intravesical pressure; PGF2 alpha produced a dose-dependent increase in both urethral and intravesical pressures. Thus it is suggested that endogenous PG release during vesical distension could play a facilitatory role in micturition.

LH, FSH, TSH, prolactin, HCG and prostaglandin F2 alpha in patients with treated testis tumors

Various kinds of treatments of testicular cancer results in significant changes in peptide hormones, particularly LH and FSH. In some cases, compensated hypothyroidism as indicated by increased TSH with normal T3 are observed. Serum levels of prostaglandin F2 alpha are also elevated after therapy without relation to the stage of the disease. During followup, these patients are found to complain of impotence and infertility, and the evaluation of serum analysis of peptide hormones must consider both the normal hormonal findings of treated testicular cancer patients and recurrence of endocrine active tumor. The hormonal changes from hypophyseal origin are secondary to the primary testicular damages in patients complaining of impotence without tumor recurrence.

Clinical experience with intravesical prostaglandin E2. A prospective study of 36 patients

In a prospective study, intravesical prostaglandins were given to 36 patients who had urinary symptoms associated with a poorly functioning detrusor; 67% of these patients were found to be in chronic retention. Using standard urodynamic techniques, 72% showed objective evidence of an immediate improvement in detrusor function and there was prolonged therapeutic benefit in 39%. A prolonged response occurred only in patients who had an intact sacral reflex arc and urodynamic evidence of a pathologically enlarged bladder, and who did not have radiologically demonstrable outflow obstruction. The use of intravesical prostaglandin to stimulate the detrusor was also found to be of value as a urodynamic technique for the investigation of the lower urinary tract.

Intravesical prostaglandin: release and effect of bladder instillation on some micturition parameters

Bladder washout effluent fluid was examined for prostaglandin-like activity following acidic lipid extraction and bioassay using the rat-stomach strips technique. A low basal level of prostaglandin-like material was detected in washouts collected when the bladder was empty in 4 out of 7 dogs. Increased levels were detected following micturition in 5 of these 7 dogs. A significantly high level of prostaglandin-like material was recovered after pelvic nerve stimulation. The prostaglandin-like material was tentatively identified as PGE based on the bioassay with the addition of specific antibody. Intravesically administered PGE2 or PFG2 alpha significantly reduced, in a dose-dependent response, the threshold micturition volume. All of these findings suggested that prostaglandins may play a role in the micturition process.

Concept of pharmacodynamics of urinary storage and micturition

The exact neuropharmacologic sequences governing continence and micturition are not yet known. Based on current investigations and those previously conducted, a concept of the anatomic, physiologic, and neuropharmacologic factors governing continence and micturition is presented.

A comparison between bromocriptine and indomethacin in the treatment of detrusor instability

Our 32 patients with urinary symptoms owing to detrusor instability (either primary or secondary to an upper motor neuron lesion) have completed a clinical trial of bromocriptine and indomethacin. Each drug was administered for 1 month, using a single blind crossover method. The symptoms and any side effects were assessed by means of a questionnaire before entry into the trial, after administration of the first drug and at the end of the trial. The improvement in diurnal and nocturnal frequency owing to indomethacin was shown by McNemar's test to be statistically highly significant.

Effects of prostaglandins on vesicourethral smooth muscle of rabbit. Therapeutic implications

The effects of PGF 2-alpha and PGE2 on the vesicourethral smooth muscle of the rabbit were studied in vitro. PGF2-alpha had potent contractile effects on the bladder body and comparatively less in the bladder base and the proximal urethra. PGE2 contractile effects were two times greater than PGF 2-alpha on the bladder body but minimal or absent on the base and the urethra. The effects of PGF2-alpha and PGE2 seem to be mediated through a prostaglandin receptor as indicated by competitive antagonism of both prostaglandins by N-0164, a synthetic phenyl phosphonate. It also appears that the effects of PGF2-alpha PGE2 may not be mediated through muscarinic, adrenergic, nicotinic, or histaminic receptors or direct smooth-muscle action. The therapeutic implications of PGE2 in the patients with problems of bladder emptying are discussed.