Involvement of β3-adrenoceptors in mouse urinary bladder function: Role in detrusor muscle relaxation and micturition reflex

The differences in the adrenergic receptors of proximal urethra between sexes

Objectives

The bladder and urethra work as a physiologically functional unit to facilitate continence in the storage and voiding phase. Sex differences have been found in the urethral contraction in response to α-adrenergic receptor activation. This study aimed to investigate the role of adrenergic receptors in the proximal urethra of male and female mice.

Materials and Methods

Urinary bladder and proximal urethral smooth muscle (USM) samples from male and female C57BL/6 mice were isolated and mounted in an organ bath.

Results

Acetylcholine-induced contraction of the urinary bladder was compared in male and female mice. Phenylephrine and norepinephrine (NE) induced little contraction at a lower concentration, but a relaxing phase of female proximal USM was observed at a higher concentration. This contraction profile was inhibited by NG-nitro-L-arginine, lidocaine, and capsaicin. In addition, the NE-induced contraction was greater in the incubation of propranolol than that of L-NNA or lidocaine. These results suggested that the β-adrenoceptor may be the dominant receptor of female proximal USM, and the activity of calcitonin gene-related peptide sensory nerves and nitrergic nerves may pose an anti-contraction effect on the proximal urethra in female mice.

Conclusion

β-adrenoceptor may be the dominant receptor of female proximal USM. The use of β-adrenergic receptor blocker agents might have the potential for the treatment of female voiding dysfunction.

β3-Adrenoceptor agonists inhibit purinergic receptor-mediated contractions of the murine detrusor

β₃-Adrenoceptor (β₃-AR) agonists are used to treat overactive bladder syndrome; however, their mechanism of action has not been determined. The aims of this study were to compare the effects of β₃-AR agonists on cholinergic versus purinergic receptor-mediated contractions of the detrusor and to examine the mechanisms underlying inhibition of the purinergic responses by β₃-AR agonists. Isometric tension recordings were made from strips of murine detrusor and whole cell current recordings were made from freshly isolated detrusor myocytes using the patch-clamp technique. Transcriptional expression of exchange protein directly activated by cAMP (EPAC) subtypes in detrusor strips was assessed using RT-PCR and real-time quantitative PCR. The β₃-AR agonists BRL37344 and CL316243 (100 nM) inhibited cholinergic nerve-mediated contractions of the detrusor by 19 and 23%, respectively, but did not reduce contractions induced by the cholinergic agonist carbachol (300 nM). In contrast, BRL37344 and CL316243 inhibited purinergic nerve-mediated responses by 55 and 56%, respectively, and decreased the amplitude of contractions induced by the P2X receptor agonist α,β-methylene ATP by 40 and 45%, respectively. The adenylate cyclase activator forskolin inhibited purinergic responses, and these effects were mimicked by a combination of the PKA activator N⁶-monobutyryl-cAMP and the EPAC activator 8-pCPT-2'-O-methyl-cAMP-AM (007-AM). Application of ATP (1 μM) evoked reproducible P2X currents in isolated detrusor myocytes voltage-clamped at -60 mV. These responses were reduced in amplitude in the presence of BRL37344 and also by 007-AM. This study demonstrates that β₃-AR agonists reduce postjunctional purinergic responses in the detrusor via a pathway involving activation of the cAMP effector EPAC.

β3-adrenoceptor agonists inhibit carbachol-evoked Ca2+ oscillations in murine detrusor myocytes

OBJECTIVE

To test if carbachol (CCh)-evoked Ca²⁺ oscillations in freshly isolated murine detrusor myocytes are affected by β3-adrenoceptor (β-AR) modulators.

MATERIALS AND METHODS

Isometric tension recordings were made from strips of murine detrusor, and intracellular Ca²⁺ measurements were made from isolated detrusor myocytes using confocal microscopy. Transcriptional expression of β-AR sub-types in detrusor strips and isolated detrusor myocytes was assessed using reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time quantitative PCR (qPCR). Immunocytochemistry experiments, using a β3-AR selective antibody, were performed to confirm that β3-ARs were present on detrusor myocytes.

RESULTS

The RT-PCR and qPCR experiments showed that β1-, β2- and β3-AR were expressed in murine detrusor, but that β3-ARs were the most abundant sub-type. The selective β3-AR agonist BRL37344 reduced the amplitude of CCh-induced contractions of detrusor smooth muscle. These responses were unaffected by addition of the BK channel blocker iberiotoxin. BRL37344 also reduced the amplitude of CCh-induced Ca²⁺ oscillations in freshly isolated murine detrusor myocytes. This effect was mimicked by CL316,243, another β3-AR agonist, and inhibited by the β3-AR antagonist L748,337, but not by propranolol, an antagonist of β1- and β2-ARs. BRL37344 did not affect caffeine-evoked Ca²⁺ transients or L-type Ca²⁺ current in isolated detrusor myocytes.

CONCLUSION

Inhibition of cholinergic-mediated contractions of the detrusor by β3-AR agonists was associated with a reduction in Ca²⁺ oscillations in detrusor myocytes.

Effect of Suo Quan Wan on the bladder function of aging rats based on the β-adrenoceptor

Suo Quan Wan (SQW) has been used to treat lower urinary tract symptoms (LUTS) in elderly patients for hundreds of years in China. β-adrenoceptors (β-ARs), particularly β₃-adrenoceptor (β₃-AR), was reported to be important in the bladder dysfunction of the elderly. The present study was conducted to explore the effect of β-AR, and particularly the β₃-adrenoceptor, in aging rat bladder function in vitro and to test the therapeutic effect of SQW on LUTS in an aging rat model based on the β₃-adrenoceptor. Briefly, the bladder detrusor muscles of young (age, 3 months) and aging (age, 15 months) female rats were separated. A β-AR non-selective agonist, isoprenaline (ISO), subtype β₃-AR agonist (BRL37344A) and β₃-AR antagonist (SR59230A) were used to define the tension change of detrusor muscles between young and aging rats in vitro. For blank controls, 12 young rats were marked, and 48 aging female rats were randomly divided into four groups as follows: Model, SQW high, SQW middle and SQW low. Following oral administration of SQW for 6 weeks in aging rats, urodynamic and bladder detrusor tests were used to evaluate the therapeutic effect of SQW. The expression of β₃-AR mRNA was investigated using reverse transcription-quantitative polymerase chain reaction. Using ISO and BRL37344A in vitro, maximum relaxation (E_max), intrinsic activity (IA), and log (50% effective concentration) (PD₂) were significantly decreased in aging rats compared with that in young rats (P<0.05). Significant changes were also observed in the β₃-AR antagonist experiment, which blocked ISO-induced relaxation, with significant decreases observed in E_max, IA and PD₂, and a significant increase observed in PA₂ for the aging rats compared with the young controls (P<0.05). SQW was demonstrated to enhance bladder control, storage and contraction ability. Furthermore, SQW was able to increase the sensitivity and expression of β₃-AR in an aging rat. In conclusion, the decrease in β₃-AR sensitivity in aging rats and the expression resulted in bladder detrusor dysfunction. In addition, the therapeutic effect of SQW against LUTS relies on the former's effect on the urethral sphincter, bladder detrusor and β₃-AR.

β-Adrenoceptor-mediated Relaxation of Urinary Bladder Muscle in β2-Adrenoceptor Knockout Mice

Background and Objective: In order to characterize the β-adrenoceptor (AR) subtypes involved in agonist-stimulated relaxation of murine urinary bladder we studied the effects of (-)-isoprenaline and CL 316,243 on tonic contraction and spontaneous contractions in detrusor strips of wild-type (WT) and β₂-AR knockout (β₂-AR KO) mice.

Materials and Methods: Urinary bladders were isolated from male WT and β₂-AR KO mice. β-AR subtype expression was determined with quantitative real-time PCR. Intact muscle strips pre-contracted with KCl (40 mM) were exposed to cumulatively increasing concentrations of (-)-isoprenaline or β₃-AR agonist CL 316,243 in the presence and absence of the subtype-selective β-AR blockers CGP 20712A (β₁-ARs), ICI 118,551 (β₂-ARs), and L748,337 (β₃-ARs).

Results: Quantitative real-time PCR confirmed lack of β₂-AR expression in bladder tissue from β₂-AR KO mice. In isolated detrusor strips, pre-contraction with KCl increased basal tone and enhanced spontaneous activity significantly more in β₂-AR KO than in WT. (-)-Isoprenaline relaxed tonic tension and attenuated spontaneous activity with similar potency, but the concentrations required were two orders of magnitude higher in β₂-AR KO than WT. The concentration-response curves (CRCs) for relaxation were not affected by CGP 20712A (300 nM), but were shifted to the right by ICI 118,551 (50 nM) and L748,337 (10 μM). The -logEC₅₀ values for (-)-isoprenaline in WT and β₂-AR KO tissue were 7.98 and 6.00, respectively, suggesting a large receptor reserve of β₂-AR. (-)-CL 316,243 relaxed detrusor and attenuated spontaneous contractions from WT and β₂-AR KO mice with a potency corresponding to the drug’s affinity for β₃-AR. L743,337 shifted the CRCs to the right.

Conclusion: Our findings in β₂-AR KO mice suggest that there is a large receptor reserve for β₂-AR in WT mice so that this β-AR subtype will mediate relaxation of tone and attenuation of spontaneous activity under physiological conditions. Nevertheless, upon removal of this reserve, β₃-AR can also mediate murine detrusor relaxation.

Mirabegron relaxes urethral smooth muscle by a dual mechanism involving β3 -adrenoceptor activation and α1 -adrenoceptor blockade

LINKED ARTICLE

This article is commented on by Michel, M. C., pp. 429-430 of this issue. To view this commentary visit http://dx.doi.org/10.1111/bph.13379.

BACKGROUND AND PURPOSE

Mirabegron is the first β3 -adrenoceptor agonist approved for treatment of overactive bladder syndrome. This study aimed to investigate the effects of β3 -adrenoceptor agonist mirabegron in mouse urethra. The possibility that mirabegron also exerts α1 -adrenoceptor antagonism was also tested in rat smooth muscle preparations presenting α1A - (vas deferens and prostate), α1D - (aorta) and α1B -adrenoceptors (spleen).

EXPERIMENTAL APPROACH

Functional assays were carried out in mouse and rat isolated tissues. Competition assays for the specific binding of [(3) H]prazosin to membrane preparations of HEK-293 cells expressing each of the human α1 -adrenoceptors, as well as β-adrenoceptor mRNA expression and cyclic AMP measurements in mouse urethra, were performed.

KEY RESULTS

Mirabegron produced concentration-dependent urethral relaxations that were shifted to the right by the selective β3 -adrenoceptor antagonist L-748,337 but unaffected by β1 - and β2 -adrenoceptor antagonists (atenolol and ICI-118,551 respectively). Mirabegron-induced relaxations were enhanced by the PDE4 inhibitor rolipram, and the agonist stimulated cAMP synthesis. Mirabegron also produced rightward shifts in urethral contractions induced by the α1 -adrenoceptor agonist phenylephrine. Schild regression analysis revealed that mirabegron behaves as a competitive antagonist of α1 -adrenoceptors in urethra, vas deferens and prostate (α1A -adrenoceptor, pA2  ≅ 5.6) and aorta (α1D -adrenoceptor, pA2  ≅ 5.4) but not in spleen (α1B -adrenoceptor). The affinities estimated for mirabegron in functional assays were consistent with those estimated in radioligand binding with human recombinant α1A - and α1D -adrenoceptors (pKi  ≅ 6.0).

CONCLUSION AND IMPLICATIONS

The effects of mirabegron in urethral smooth muscle are the result of β3 -adrenoceptor agonism together with α1A and α1D -adrenoceptor antagonism.

β-Adrenoceptor-Mediated Relaxation of Carbachol-Pre-Contracted Mouse Detrusor

Aims: To study the β-adrenoceptor subtypes involved in the relaxation responses to (-)-isoprenaline in carbachol-pre-contracted (CCh) mouse detrusor muscle with intact and denuded mucosa. Methods: Isolated muscle strips from the urinary bladder of male C57BL6 mice or β2-adrenoceptor knockout mice were pre-contracted with CCh, 1 µM and relaxed with increasing concentrations of the β-adrenoceptor (β-AR) agonist (-)-isoprenaline and forskolin. For estimating the β-AR subtypes involved, subtype-selective receptor blockers were used, that is, CGP 20712A (β1-ARs), ICI 118,551 (β2-ARs), and L748,337 (β3-ARs). Results: Unlike in KCl-pre-contracted muscle, the mucosa did not affect the sensitivity of the relaxation response to (-)-isoprenaline in CCh-pre-contracted murine detrusor strips. Increasing concentrations of (-)-isoprenaline produced a biphasic concentration-relaxation response without any difference both during the presence and absence of mucosa. The relaxation fraction produced by low (-)-isoprenaline concentrations was mediated by β2-AR as evidenced by a shift of the concentration-response curve to higher concentrations with ICI 118,551, but not with CGP 20712A and L748,337, and by the absence of this fraction in β2-AR-KO mice. The relaxation response with low sensitivity to (-)-isoprenaline was not affected by any of the β-AR subtype-selective blockers and was the only response detected in detrusor strips from β2-AR-KO mice. Conclusions: In CCh-pre-contracted mouse detrusor, β2-ARs are responsible for the relaxation component with high sensitivity to (-)-isoprenaline as indicated by the conversion of a biphasic into a monophasic CRC with ICI 118,551 or by its absence in β2-AR KO mice. The mucosa does not impair relaxation under these conditions.

Blockade of renin-angiotensin system prevents micturition dysfunction in renovascular hypertensive rats

Association between hypertension and bladder symptoms has been described. We hypothesized that micturition dysfunction may be associated with renin-angiotensin system (RAS) acting in urethra. The effects of the anti-hypertensive drugs losartan (AT1 antagonist) and captopril (angiotensin-converting enzyme inhibitor) in comparison with atenolol (β1-adrenoceptor antagonist independently of RAS blockade) have been investigated in bladder and urethral dysfunctions during renovascular hypertension in rats. Two kidney-1 clip (2K-1C) rats were treated with losartan (30 mg/kg/day), captopril (50mg/kg/day) or atenolol (90 mg/kg/day) for eight weeks. Cystometric study, bladder and urethra smooth muscle reactivities, measurement of cAMP levels and p38 MAPK phosphorylation in urinary tract were determined. Losartan and captopril markedly reduced blood pressure in 2K-1C rats. The increases in non-voiding contractions, voiding frequency and bladder capacity in 2K-1C rats were prevented by treatments with both drugs. Likewise, losartan and captopril prevented the enhanced bladder contractions to electrical-field stimulation (EFS) and carbachol, along with the impaired relaxations to β-adrenergic-cAMP stimulation. Enhanced neurogenic contractions and impaired nitrergic relaxations were observed in urethra from 2K-1C rats. Angiotensin II also produced greater urethral contractions that were accompanied by higher phosphorylation of p38 MAPK in urethral tissues of 2K-1C rats. Losartan and captopril normalized the urethral dysfunctions in 2K-1C rats. In contrast, atenolol treatment largely reduced the blood pressure in 2K-1C rats but failed to affect the urinary tract smooth muscle dysfunction. The urinary tract smooth muscle dysfunction in 2K-1C rats takes place by local RAS activation irrespective of levels of arterial blood pressure.

Mucosa of murine detrusor impairs β2 -adrenoceptor-mediated relaxation

AIMS

To investigate the role of the mucosa in (-)-isoprenaline-induced relaxation of mouse detrusor muscle and to characterize the β-adrenoceptor subtypes involved.

METHODS

Isolated intact and mucosa-denuded muscle strips from the urinary bladder of male C57BL6 mice were pre-contracted with KCl (40 mM) and were relaxed with increasing concentrations of the β-adrenoceptor (β-AR) agonist (-)-isoprenaline and forskolin in the presence and absence of the subtype-selective β-AR blockers CGP20712A (β1 -ARs), ICI118,551 (β2 -ARs), and L748,337 (β3 -ARs).

RESULTS

Force development in response to KCl was larger in mucosa-denuded than in intact preparations and was almost completely relaxed with increasing concentrations of (-)-isoprenaline. Mucosa-denuded muscles were about 10-fold more sensitive to (-)-isoprenaline than intact muscles. CGP20712A did not affect the concentration-response curves (CRCs) to (-)-isoprenaline, ICI118,551 shifted the CRC further to the right in denuded than in intact strips so that the difference between them was abolished. Combined exposure to β1 -AR and β2 -AR blocker yielded the same result. L748,337 did not significantly affect the CRC to (-)-isoprenaline but caused additional blockade to ICI118,551 in the presence of intact mucosa.

CONCLUSIONS

The mucosa of mouse detrusor strips impairs KCl-induced force development and reduces the sensitivity to β-AR-induced relaxation. The relaxing response to (-)-isoprenaline as well as the mucosa effect thereupon are mainly mediated by β2 -ARs. A minor involvement of β3 -ARs becomes apparent particularly at high (-)-isoprenaline concentrations.

The new radioligand [(3)H]-L 748,337 differentially labels human and rat β3-adrenoceptors

As no suitable radioligand exists for the detection of β3-adrenoceptors, we have explored the radioligand binding properties of a tritiated version of the selective β3-adrenoceptor antagonist L 748,337. Kinetic and equilibrium saturation and competition binding experiments were performed with [(3)H]-L 748,337 on membrane fractions of HEK and CHO cells stably transfected with human and rat β-adrenoceptor subtypes. Based on both association/dissociation kinetic and equilibrium saturation binding studies in transfected HEK cells, [(3)H]-L 748,337 exhibited an affinity of approximately 2 nM for human β3-adrenoceptors. Competition studies with agonists and subtype-selective antagonists validated its binding to β3-adrenoceptors. In CHO cells transfected with human β3-adrenoceptors similar saturable high-affinity of [(3)H]-L 748,337 was observed. While some isoprenaline-sensitive [(3)H]-L 748,337 binding was also observed in CHO cells transfected with human β1- or β2-adrenoceptors, this was not saturable in a similar concentration range and/or not sensitive to the antagonists propranolol and SR 59,230, indicating that it did not primarily involve β-adrenoceptors. In CHO cells transfected with rat β3-adrenoceptors [(3)H]-L 748,337 exhibited a considerably lower affinity than with the human subtype (12-95 nM). Low affinity for the rat β3-adrenoceptor was also found with unlabelled L 748,337 in rat bladder strip relaxation experiments. We conclude that L 748,337 apparently has lower affinity for the rat than the human β3-adrenoceptors and that [(3)H]-L 748,337 can bind to a low-affinity site distinct from the orthosteric pocket of β-adrenoceptors. Nevertheless, [(3)H]-L 748,337 appears to be the most promising radioligand for the selective labelling of human β3-adrenoceptors reported to date.

A functional analysis of the influence of β3-adrenoceptors on the rat micturition cycle

Dysfunctions of the lower urinary tract, such as overactive bladder syndrome and incontinence, are the product of storage failure. Spontaneous regional bladder wall movements [nonmicturition contractions (NMCs)] are proposed to generate afferent activity that signals volume status to the central nervous system. The sympathetic nervous system, via activation of β-adrenoceptors (β-ARs), causes bladder relaxation and promotes urine storage. We hypothesized that β-AR regulation of micturition is mediated by suppression of NMCs. We used an unanesthetized, decerebrate, artificially perfused rat preparation that allows simultaneous cystometry with external urethral sphincter and pelvic afferent nerve recordings. Systemic isoprenaline (10 nM to 1 µM) increased intervoid interval and bladder compliance accompanied by a decrease in NMC amplitude, voiding pressure, and voiding threshold. Isoprenaline also reduced arterial pressure and increased heart rate. The β3-AR agonist mirabegron (10-100 nM) increased intervoid interval and bladder compliance and reduced NMC amplitude, yet preserved active voiding function and had no effect on arterial pressure or heart rate. All of these effects of mirabegron were blocked by the selective β3-AR antagonist N-[[3-[(2S)-2-hydroxy-3-[[2-[4-[(phenylsulfonyl)amino] phenyl]ethyl]amino]propoxy]phenyl]methyl]-acetamide (L748,337), which alone shortened intervoid interval and decreased bladder compliance-suggesting the presence of a basal β3-AR-mediated sympathetic tone. Similar effects of mirabegron were seen in an acetic acid-sensitized bladder preparation and in preparations after loss of spinobulbar reflex bladder control. The β3-AR-mediated increase in intervoid interval correlated with increased bladder compliance but not with the decrease in NMC amplitude. These findings indicate that β3-adrenoceptors have a selective effect that improves urine storage by increasing compliance without affecting the active components of voiding.

Fenoterol functionally activates the β₃-adrenoceptor in human urinary bladder, comparison with rat and mouse: implications for drug discovery

Fenoterol has been reported to be a potent and selective β(2)-adrenoceptor agonist and is currently used clinically to treat asthma. Electrical field stimulation (EFS) of isolated urinary bladder mimics the voiding contraction by stimulating parasympathetic nerves, resulting in neurogenic contractions. To determine if stimulation of β(2)-adrenoceptors can inhibit this response, fenoterol was tested against EFS-induced contractions in human isolated urinary bladder and compared with mouse and rat. Bladder strips were mounted in organ baths and reproducible contractions induced by EFS. Fenoterol was added cumulatively in the presence of the β(2)-adrenoceptor antagonist ICI118551 or the β(3)-adrenoceptor antagonist L-748337. Fenoterol inhibited neurogenic contractions in all three species in a concentration-dependent manner with pEC(50) values of 6.66 ± 0.11, 6.86 ± 0.06 and 5.71 ± 0.1 in human, mouse and rat respectively. In human bladder strips ICI118551 (100 nM) did not affect responses to fenoterol, while L-748337 (0.3-3 μM) produced rightward shifts of the concentration-response curves with a pA(2) value of 8.10. In mouse bladder strips ICI118551 (30 nM) blocked the inhibitory effect of fenoterol (pA(2)=8.80), while L-748337 (10 μM) inhibited the response with a pA(2) of 5.79. In rat bladder ICI118551 (30 nM) was without effect, while L-748,337 (10 μM) inhibited the response to fenoterol with a pA(2) of 5.40. From these results it is clear that fenoterol potently activates β(3)-adrenoceptors in human isolated urinary bladder to inhibit EFS-induced contractions. Fenoterol also activates β(3)-adrenoceptors in rat, but β(2)-adrenoceptors in mouse bladder to inhibit EFS-induced contractions.

Do β3-adrenergic receptors play a role in guinea pig detrusor smooth muscle excitability and contractility?

In many species, β3-adrenergic receptors (β3-ARs) have been reported to play a primary role in pharmacologically induced detrusor smooth muscle (DSM) relaxation. However, their role in guinea pig DSM remains controversial. The aim of this study was to investigate whether β3-ARs are expressed in guinea pig DSM and to evaluate how BRL37344 and L-755,507, two selective β3-AR agonists, modulate guinea pig DSM excitability and contractility. We used a combined experimental approach including RT-PCR, patch-clamp electrophysiology, and isometric DSM tension recordings. β3-AR mRNA message was detected in freshly isolated guinea pig DSM single cells. BRL37344 but not L-755,507 caused a slight decrease in DSM spontaneous phasic contraction amplitude and frequency in a concentration-dependent manner. In the presence of atropine (1 μM), only the spontaneous phasic contractions frequency was inhibited by BRL37344 at higher concentrations. Both BRL37344 and L-755,507 significantly decreased DSM carbachol-induced phasic and tonic contractions in a concentration-dependent manner. However, only BRL37344 inhibitory effect was partially antagonized by SR59230A (10 μM), a β3-AR antagonist. In the presence of atropine, BRL37344 and L-755,507 had no inhibitory effect on electrical field stimulation-induced contractions. Patch-clamp experiments showed that BRL37344 (100 μM) did not affect the DSM cell resting membrane potential and K(+) conductance. Although β3-ARs are expressed at the mRNA level, they play a minor to no role in guinea pig DSM spontaneous contractility without affecting cell excitability. However, BRL37344 and L-755,507 have pronounced inhibitory effects on guinea pig DSM carbachol-induced contractions. The study outlines important DSM β3-ARs species differences.

Hyperthyroidism and female urinary incontinence: a population-based cohort study

OBJECTIVE

The imbalanced autonomic nervous system present in hyperthyroidism may cause lower urinary tract symptoms. Urinary incontinence (UI) is the most bothersome lower urinary tract symptom; however, in the literature, reports regarding urinary dysfunction and/or incontinence among hyperthyroid patients are scarce. This population-based cohort study aimed to examine the relationship between hyperthyroidism in women and the risk of developing UI in Taiwan.

DESIGN

This study used data from the Longitudinal Health Insurance Database. For this study, 10,817 female patients diagnosed with hyperthyroidism from 2001 to 2005 were recruited together with a comparison cohort of 54,085 matched enrollees who did not have a history of hyperthyroidism. All patients were tracked for a 3-year period from their index date to identify those who had a subsequent UI. The stratified Cox proportional hazards models were used to compute the risk of UI between study and comparison cohorts.

RESULTS

During the follow-up period, of 64,169 patients, 173 (1·60%) from the hyperthyroidism group and 560 (1·04%) from the comparison group, had a diagnosis of UI. The regression analysis showed that, after adjusting for monthly income, geographic region, urbanization level of the community in which the patient resided, obesity and hysterectomy, patients with hyperthyroidism were more likely to have UI during the 3-year follow-up period than the comparison patients (hazard ratio = 1·54; 95% CI = 1·30-1·83; P < 0·001).

CONCLUSION

Our results suggest an increased risk of UI in patients with hyperthyroidism at the 3-year follow-up.

β-Adrenoceptor-mediated differences in transverse and longitudinal strips from the rat detrusor

Contractions and relaxations of the urinary bladder occur in all directions to facilitate urine release and storage. Transverse and longitudinal contractility of detrusor smooth muscle have been studied before using various pharmacologic stimuli but not β agonists. Given the importance of β-adrenoceptors in mediating bladder relaxation, the effects of isoprenaline (IPNA) in transverse and longitudinal contractility were examined. Pretreatment with a low concentration of IPNA (0.1 or 1 μM) suppressed carbachol (CCh)-induced contractions, more in the transverse than longitudinal direction. Increasing the IPNA concentration to 10 or 100 μM resulted in greater inhibition of longitudinal contractions. Also in the longitudinal direction, IPNA-induced relaxation was greater than in the transverse direction. When precontracted with a submaximal concentration of CCh (1 μM), IPNA increased the phasic activity in the longitudinal direction only. In summary, β-adrenoceptor-mediated differences between transverse and longitudinal contractility were revealed. In testing the relaxant properties of selective β-agonists, the findings here should be considered such that other than the conventional longitudinal contractions, measurements are also made in other directions.