Beta-adrenoceptor subtypes in the ureteral smooth muscle of rats, rabbits and dogs

In vitro effects of β3-adrenoceptor agonist mirabegron on the human ureter

INTRODUCTION

This study aimed to investigate the effect of mirabegron, a β3-adrenoceptor agonist with widespread clinical use for treating overactive bladder disease, on isolated healthy human ureter strips.

MATERIALS AND METHODS

This was a prospective study employing a series of in vitro organ bath experiments using ureteral tissues of kidney grafts from 10 healthy donors. The ureteral strips were subjected to cumulative mirabegron concentrations (10-9-10-4.5 M). Effects on frequency or amplitude of spontaneous, 10 mM KCl- or EFS-induced contractions were evaluated.

RESULTS

Mirabegron decreased the frequency of spontaneous ureteric contraction in a concentration-dependent manner. Statistically significant decrease in the frequency of spontaneous contraction was observed at 10-8-10-4.5 M. In 10 mM KCl medium, statistically significant change in frequency was observed at 10-9-10-4.5 M. Statistically significant decrease in the amplitudes of spontaneous contraction was observed at 10-7-10-4.5 M. In a 10 mM KCl medium, statistically significant change in amplitudes was observed at 10-8-10-4.5 M.

CONCLUSIONS

Mirabegron reduced the amplitude and frequency of human ureter activity in in vitro organ bath studies. This effect was achieved in a dose-dependent manner on isolated tissue strips. Although monotherapy with mirabegron remains uncertain, this study has the potential to elucidate the mechanism underlying the effectiveness of mirabegron, particularly in combination therapy for ureteral stones.

The modulation of ureteral smooth muscle contractile responses by α1- and α2-adrenoceptor activation

PURPOSE

This study was performed to investigate the influence of α-adrenoceptor subtypes upon ureteral smooth muscle contractile responses.

METHODS

Rat ureters were challenged in vitro with noradrenaline (NA), the α₁-adrenoceptor agonist phenylephrine (PE), and the α₂-adrenoceptor agonist clonidine (CLON). The influences of the agonists on the magnitude and frequency of acetylcholine (ACh)-stimulated phasic contractile responses were recorded.

RESULTS

The magnitude of the phasic contractile responses effected by ACh was not significantly influenced by the adrenoceptor agonists, but the frequency of the response was significantly enhanced by all three agonists (p < 0.05). Idazoxan and prazosin abolished the rise in frequency effected by CLON and PE, respectively, whereas both antagonists in combination were required to abolish the increase in frequency effected by NA.

CONCLUSIONS

It has been demonstrated that α₁- and α₂-adrenoceptors modulate the contractile function of rat ureteral smooth muscle by increasing the frequency, but not the magnitude, of phasic contractile responses. The enhancement of contractile function by NA is mediated by mechanisms dependent upon both α₁- and α₂-adrenoceptors.

Pressure matters 2: intrarenal pressure ranges during upper-tract endourological procedures

PURPOSE

To perform a review on the latest evidence related to intrarenal pressures (IRPs) generated during upper-tract endourology, and present different tools to maintain decreased values, to decrease complication rates.

METHODS

A literature search was performed using PubMed, restricted to original English-written articles, including animal, artificial model and human studies. Different keywords were: percutaneous nephrolithotomy, PCNL, ureteroscopy, URS, RIRS, irrigation flow, irrigation pressure, intrarenal pressure, intrapelvic pressure and renal-pelvic pressure.

RESULTS

IRPs reported during retrograde intrarenal surgery (RIRS), PCNL, miniPCNL, and microPCNL range 40.8-199.35, 3-40.8, 10-45 and 15.37-41.21 cm H₂O, respectively. By utilizing ureteral access sheaths (UASs) IRPs usually remain lower than 30 cm H₂O at an irrigation pressure (IP) of ≤ 100 cm H₂O but could increase to > 40 cm H₂O at an IP of 200 cm H₂O. By utilizing the minimally invasive PCNL system, IRPs remain low at 20 cm H₂O even at high IPs. Utilizing endoluminal isoproterenol during RIRS, could reduce IRP increases with a rate of 27-107%, and maintain low IRPs values, usually below 50 cm H₂O.

CONCLUSIONS

Increased IRP values have been reported during RIRS and UASs constitute the most efficient tool for decreasing them. IRPs during mini-PCNL can be decreased utilizing the vacuum-cleaner and purging effects but might remain uncontrolled during micro- and ultra-mini PCNL. Intraluminal pharmacological treatment could play a role in IRP decrease, with isoproterenol being the most studied agent.

Does the endoscopic treatment of lower ureter stones affect uroflowmetric values? A prospective clinical trial

OBJECTIVES

The aim of this study was to document if stones at the lower ureter alter the micturition capability of the patients and to investigate whether endoscopic removal of these stones restores normal urinary flow rates or not in the 3 months of follow-up.

METHODS

Forty patients with lower ureteral stone (group 1) and 20 control subjects with proximal ureteral stone (group 2) were enrolled into the study. All patients underwent uroflowmetry testing before and 3 months after the treatment for endoscopic stone removal. The mean average and peak flow rates with a sufficient voided volume (≥150 ml) were evaluated before and after surgery and compared between the groups.

RESULTS

Mean values of the peak flow rates before and after surgery were 20.3 and 27.5 ml/s in group 1 and 22.5 and 23.6 ml/s in group 2, and the mean average flow rate values before and after surgery were 10.5 and 13.6 ml/s in group 1 and 11.4 and 12.1 ml/s in group 2. Statistically significant differences were determined between before and after ureteroscopy values were determined in terms of average (p < 0.05) and peak flow rates (p < 0.01) in group I; however, there no significant difference was seen in the control group.

CONCLUSION

We document for the first time in the literature that patients with lower ureteric stones have a reduction in their urinary stream which resolves with endoscopic removal of the stones.

Ureterovesical junction obstruction causes increment in smooth muscle contractility, and cholinergic and adrenergic activity in distal ureter of rabbits

BACKGROUND/PURPOSE

The controversy in management of primary obstructed megaureter necessitates further elucidation of the underlying pathophysiology. We evaluated smooth muscle contractility, and cholinergic, adrenergic and serotonergic activity of rabbit distal ureters after ureterovesical junction (UVJ) obstruction.

METHODS

Sham (SH) operation, partial obstruction (PO) and complete obstruction (CO) of the right UVJ were performed in rabbits. Three weeks later, distal ureters were isolated; spontaneous contractions (SC), contractile responses to electrical field stimulation (EFS), high KCl, carbachol, phenylephrine and serotonin were recorded.

RESULTS

SC amplitudes increased in CO compared to PO and SH (p<0.001). SC frequency was higher in CO (p<0.05). EFS-induced contraction amplitudes were greater in CO than other groups (p<0.05). High KCl-induced contractions were greater in CO (p<0.001) and PO (p<0.01). Carbachol-induced contractility was enhanced in CO and PO (p<0.05). Contractile response to phenylephrine was greater in CO than other groups (p<0.05). Serotonin induced contractile responses in CO and PO, greater in CO (p<0.05). UVJ obstruction also increased spontaneous contractility in contralateral PO and CO ureters.

CONCLUSIONS

UVJ obstruction increased spontaneous and neurotransmitter-induced contractions in an obstruction grade-dependent manner. Obstruction also altered contractility of the contralateral ureters. Our findings may serve to provide further understanding of the pathophysiology of megaureter.

β(3) Receptors: Role in Cardiometabolic Disorders

Pharmacological and molecular approaches have shown that an atypical β-adrenoceptor (AR), called β(3)-AR, that is distinct from β(1)-ARs and β(2)-ARs, exists in some tissues in heterogeneous populations such as β(3a)-ARs and β(3b)-ARs. β(3)-ARs belong to a superfamily of receptors linked to guanine nucleotide binding proteins (G proteins). The β(3)-AR gene contains two introns whereas the β(1)-AR and β(2)-AR genes are intronless, leading to splice variants. β(3)-ARs can couple to G(i) and G(s) and they are reported to be present in brown adipose tissue, vasculature, the heart, among other tissues. β(3)-ARs cause vasodilation of microvessels in the islets of Langerhans and may participate in the pathogenesis of cardiac failure, during which modification of β(1)-AR and β(2)-AR expression occurs. The development of β(3)-AR agonists has led to the elaboration of promising new drugs, including antiobesity and antidiabetic drugs. This article reviews the various pharmacological actions of β(3)-ARs and their clinical implications for diabetes and cardiovascular diseases.

β-Adrenergic Receptor Subtypes in the Urinary Tract

Within the urinary tract, β-adrenergic receptors (AR) are found largely on smooth muscle cells but are also present, at least in the bladder, in the urothelium and on afferent nerves. Our understanding of β-AR subtype expression and function is hampered by a lack of well-validated tools, particularly with regard to β(3)-AR. Moreover, the β-AR subtypes involved in a specific function may differ between species. In the ureter, β-AR can modulate pacemaker activity and smooth muscle tone involving multiple subtypes. In the human bladder, β-AR promote urine storage. Bladder smooth muscle relaxation primarily involves β(3)-AR, and the agonists selective for this subtype are in clinical development to treat bladder dysfunction. While prostate and urethra also express β-AR, the overall physiological role in these tissues remains unclear.

[Ureter drugs]

Many improvements have been made recently in the field of the ureteral smooth muscle pharmacology. After a brief summary on physiological basis, we review what is known about effects on ureter of different drugs class. In a second part, we review clinical applications for renal colic analgesia, calculi expulsive medical therapy, ESWL adjuvant treatment and preoperative treatment before retrograde access. There are now sufficient data on NSAID and alpha-blockers. beta-agonists, especially for beta3 selective ones, and topical drugs before retrograde access are interesting and should be further evaluated.

Doxazosin relaxes ureteral smooth muscle and inhibits epinephrine-induced ureteral contractility in vitro

OBJECTIVES

Although recent evidence has supported increased ureteral stone passage with selective alpha(1)-adrenergic receptor antagonists, no mechanistic study evaluating ureteral relaxation by alpha(1) antagonism has been reported to date. We evaluated whether the alpha-blocker doxazosin reduces spontaneous, and inhibits alpha(1)-agonist-induced ureteral contractility. Additionally, alpha-receptor subtypes in normal and obstructed human ureter were analyzed.

METHODS

We exposed porcine ureters in organ tissue baths with 0.1, 1.0, or 10 microM doxazosin and recorded the tension for 90 minutes. After the initial treatment, a concentration-response curve of epinephrine or phenylephrine (1 nM to 10 microM) was generated. The experiment was repeated with the proximal, mid-, and distal ureter. The relative expression of the alpha 1A, 1B, and 1D receptor subtypes in normal and obstructed human ureters was analyzed using immunoblotting.

RESULTS

Doxazosin reduced the spontaneous ureteral contractility rates in a concentration-dependent fashion by 23% to 34%. A more pronounced relaxation effect by doxazosin was evident when epinephrine was introduced to the tissues. In 1 and 10-microM doxazosin-pretreated tissues, epinephrine caused 89% and 100% relaxation, respectively. Phenylephrine-induced contractions were antagonized by doxazosin but not reversed to any relaxant function. No differential expression of alpha(1)-receptor subtypes was identified in the obstructed versus normal ureters.

CONCLUSIONS

The results of our study have shown that alpha(1)-receptor blockade decreases ureteral contractility and inverses the effect of epinephrine, providing even greater relaxation. We hypothesize that alpha receptor blockade might relax the ureter and induce stone passage by way of epinephrine activation of beta receptors. Additional studies should be performed to validate this hypothesis and to compare various alpha(1)-receptor subtype antagonists.

Local and systemic effects of endoluminal pelvic perfusion of isoproterenol: a dose response investigation in pigs

PURPOSE

Isoproterenol (Sygehus Apotekerne Danmark, Copenhagen, Denmark) is a beta-adrenergic agonist known to cause upper urinary tract relaxation. We studied the local effect on pelvic pressure and the systemic effects of endoluminal perfusion with isoproterenol in a porcine model.

MATERIALS AND METHODS

Pigs weighing 40 kg were studied. Catheters were placed in the renal pelvis for pressure measurement and perfusion, and a catheter was used to drain the bladder. Blood pressure and heart rate were recorded. In 6 pigs in group 1 the pelvic pressure increase was examined at increasing flow rates of 0, 2, 5, 8, 10 and 15 ml per minute with saline containing 0, 10(-3), 10(-2), 10(-1), 1 and 10 microg/ml isoproterenol. Blood values of isoproterenol were analyzed. In 6 pigs in group 2 the pelvis was perfused at a flow rate of 8 ml per minute with saline containing 0, 10(-5), 10(-4), 10(-3), 10(-2), 10(-1), 1 and 10 microg/ml isoproterenol.

RESULTS

In group 1 endoluminal perfusion with isoproterenol inhibited the pelvic pressure increase due to perfusion at all concentrations of isoproterenol. At a perfusion rate of 8 ml per minute the maximal effect (a 78% decrease) was achieved using 0.1 microg/ml isoproterenol without cardiovascular side effects. In group 2 all isoproterenol concentrations caused significant inhibition of the pressure-flow relationship in a dose dependent matter. A 64% decrease in the pressure increase due to saline perfusion was achieved at 0.1 microg/ml isoproterenol without concomitant significant cardiovascular side effects. Isoproterenol was only detected in plasma during perfusion with 1 and 10 microg/ml isoproterenol, which caused significant cardiovascular side effects in the latter case.

CONCLUSIONS

Isoproterenol significantly inhibits the pressure increase due to perfusion in the normal porcine renal pelvis without concomitant cardiovascular side effects. Isoproterenol is a safe drug in this porcine model and, hence, it is potentially useful during endourological procedures.

In vitro analysis of the effect of hyperbilirubinemia on rabbit ureter and bladder

Spontaneous resolution of intrauterine pelvic dilatations after birth is an expected outcome. In nonobstructive pelvic dilatations, changes in ureteral and bladder physiology may also play a part. We aimed to demonstrate the effect of increased concentrations of bilirubin on ureteral and bladder muscles in vitro. Normal and pathologic concentrations of bilirubin (3.5x10(-7)-10(-5)M and 10(-4)-4x10(-4)M, respectively) caused no change in the basal ureter tension (343.9+/-29.4 mg). Normal concentrations of bilirubin caused no difference in basal bladder tension (430.2+/-70.2 mg), but pathologic concentrations caused a decrease of 303.8+/-52.9 mg. Normal and pathologic amounts of bilirubin were cumulatively applied to rabbit ureteral and bladder tissues both after reaching basal tension and when contracted with KCl (80 mM and 120 mM KCl for ureter and bladder, respectively). The cumulative addition of normal bilirubin concentrations to the ureteral tissues precontracted with KCl produced 86.4+/-7.2% relaxation, while the addition of pathologic bilirubin concentrations produced a relaxation of 133.9+/-17.4%, which was significantly higher (p=0.04). Similarly, the addition of normal concentrations of bilirubin to the bladder tissues precontracted with KCl produced a maximal relaxation of 35.3+/-2.2%, while pathologic concentrations produced a maximal relaxation of 53.5+/-3.5%, which was significantly higher (0.001). Consequently, high concentrations of bilirubin caused a mild relaxation in basal ureteral and bladder tensions, while pathologically increased concentrations led to significant relaxation in both types of precontracted tissues. We suggest that high bilirubin levels may partly but not directly contribute to the spontaneous recovery of hydronephrosis because of the relaxation effect on bladder while probably causing susceptibility to urinary tract infections because of relaxation of both ureteral and bladder tissues.

Goat ureter-an alternative model for measuring ureteral peristalsis

An alternative model for the measurement of ureteral peristalsis is described using the goat ureter. Ureters from freshly slaughtered goats (Capra aegagous hircus) were collected from a local slaughter house. The peristaltic reflex of these preparations was recorded using a specially designed apparatus. The preparations were mounted so that contractile responses to drugs could be recorded isometrically. Histological studies were undertaken to enable a correlation to be made between the anatomical observations and the functional studies. The spontaneous peristaltic reflex of the goat ureter (7 +/- 2 per 2 min) showed a 50% increase in the frequency of contraction (13.66 +/- 1.6, P<0.001) after application of histamine at a concentration of between 6.512 microM and 13.024 microM, but was blocked completely by 10.4 microM of pheniramine (P>0.05). The reflex was not blocked by the H2 blocker ranitidine (P<0.001). The effects of acetylcholine were variable. Calcium chloride at 6.8 microM resulted in a tetanic response (P<0.001). Nicorandil showed partial inhibition of spontaneous peristaltic reflex at 189.4 microM and complete inhibition at 473.4 microM (P<0.001). Although acetylcholine did not show any appreciable effect on the isometric contractions at a maximum dose of 275.2 microM, adrenaline increased the frequency of contractions by 8.2 +/- 6.5 (P<0.001), while salbutamol and isoprenaline had no effect. The histology revealed a striking resemblance to the human ureter, with a structure that explained the responses obtained. The anatomic, physiologic and histological similarities to the human ureter make it an effective alternative in tropical countries for research on ureteral peristalsis.

The potency of KUL-7211, a selective ureteral relaxant, in isolated canine ureter: comparison with various spasmolytics

We compared the potency of a selective ureteral relaxant KUL-7211 (beta(2)/beta(3)-adrenoceptor agonist; (-)-2-[4-(2-{[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amino}ethyl)phenyloxy]acetic acid) with those of various spasmolytics on contractions in isolated canine ureteral preparations. Drug effects were evaluated on the tonic contraction induced by KCl (80 mM) and on spontaneous, 1x10(-5) M phenylephrine-, and 1x10(-6) M PGF(2alpha)-induced rhythmic contractions in isolated canine ureteral preparations using a functional experimental technique. The potencies (pD(2) value) of the following drugs were compared: KUL-7211, tamsulosin (an alpha(1A/1D)-adrenoceptor antagonist), prazosin (an alpha(1)-adrenoceptor antagonist), verapamil (a Ca(2+)-channel blocker), butylscopolamine (a nonselective muscarinic antagonist), and papaverine (a phosphodiesterase inhibitor). The rank order of relaxing potencies against KCl-induced tonic contraction was KUL-7211 (6.60)>tamsulosin(5.90)>verapamil(5.70)>papaverine(4.88)>prazosin (4.54). The rank order of potencies for reductions in spontaneous rhythmic contractions was KUL-7211 (6.80)>verapamil(6.12)>papaverine(5.05). Conversely, high concentrations of the two alpha-adrenoceptor antagonists (tamsulosin and prazosin) and of butylscopolamine enhanced the spontaneous contractions, although at low concentrations (up to 1x10(-6) M) they had no significant effects. For suppression of spasmogen-induced rhythmic contractions, the rank order of potencies was, against phenylephrine-induced contractions: KUL-7211 (6.95)>tamsulosin(6.26)>prazosin(5.68)>verapamil(5.64)>papaverine (5.03), and against PGF(2alpha)-induced contractions: KUL-7211 (7.05)>verapamil(6.70)>papaverine (5.27). Our results suggest that in dogs, the beta(2)/beta(3)-adrenoceptor agonist KUL-7211 is the most efficacious ureteral relaxant among the spasmolytics tested against various contractions. Possibly, KUL-7211 might be useful for promoting stone passage and relieving ureteral colic in urolithiasis patients.

PHARMACOLOGICAL CHARACTERIZATION OF β-ADRENOCEPTOR SUBTYPES MEDIATING RELAXATION IN PORCINE ISOLATED URETERAL SMOOTH MUSCLE

PURPOSE

We pharmacologically characterized the functional beta-adrenoceptor subtypes mediating porcine ureteral smooth muscle relaxation.

MATERIALS AND METHODS

The effects of various beta-adrenoceptor agonists and antagonists on KCl induced tonic contractions in isolated porcine ureteral preparations were evaluated using a functional experimental technique.

RESULTS

The rank order of potency for the catecholamines tested was isoprenaline > adrenaline > noradrenaline. All beta2-adrenoceptor agonists tested (salbutamol, procaterol and terbutaline) attenuated the KCl induced contraction. The 2 beta3-adrenoceptor agonists CL-316243 ((R, R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethylamino]propyl]-1,3-benzodioxole-2,2-dicarboxylate], Kissei, Nagano, Japan) and CGP-12177A ((+/-)[4-[3[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2 H-benzimidazol-2-one hydrochloride], Funakoshi, Tokyo, Japan) also relaxed the ureter. The beta1-adrenoceptor agonist dobutamine had a relaxing effect on the ureter only at high concentrations (over 1 x 10 M). Isoprenaline induced relaxation was antagonized by the beta2-adrenoceptor antagonist ICI-118,551 ((+/-)-1-[(2,3-dihydro-7-methyl-1 H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride, Sigma, St. Louis, Missouri) but not by the beta1-adrenoceptor antagonist CGP 20712A ((+/-)-2-hydroxy-5-[2-[[2-hydroxy-3-[4-[1-methyl-4-(trifluoromethyl)-1 H-imidazol-2-yl]phenoxy]propyl]amino]ethoxy]-benzamide methanesulphonate, Funakoshi). In the presence of 1x 10 M CGP 20712A plus 1 x 10 M ICI-118,551 the beta3-adrenoceptor antagonist SR 58894A (3-(2-allylphenoxy)-1-[(1 S)-1,2,3,4-tetrahydronaphth-1-ylamino]-(2 S)-2-propanol hydrochloride, Kissei) antagonized isoprenaline induced relaxation.

CONCLUSIONS

Our results suggest that porcine ureteral smooth muscle is relaxed by beta2 and beta3-adrenergic stimulation, as in humans.

Pharmacological profile of KUL-7211, a selective beta-adrenoceptor agonist, in isolated ureteral smooth muscle

Since, in the human ureter, both beta(2)- and beta(3)-adrenoceptors mediate adrenergic-stimulation-induced relaxation, selective beta(2)-/beta(3)-adrenoceptor agonists might prove clinically useful for relieving ureteral colic and promoting stone passage. We evaluated the beta-adrenoceptor subtype selectivity and ureteral-relaxing efficacy of (-)-2-[4-(2-[[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amin] ethyl)phenyloxy]acetic acid (KUL-7211), a new beta-adrenoceptor agonist, in vitro. In rat isolated organs, its selectivities, for inhibition of spontaneous uterine contraction (mediated via beta(2)-adrenergic stimulation) and inhibition of colonic contraction (via beta(3)-adrenergic stimulation) versus increase in atrial rate (via beta(1)-adrenergic stimulation), were 56.3 and 242.2, respectively. KUL-7211 relaxed 80-mM-KCl-induced tonic contractions in both rabbit (pD(2) value: 5.86 +/- 0.13, whose ureteral relaxation is mediated via beta(2)-adrenergic stimulation) and canine (pD(2) value: 6.52 +/- 0.16, via beta(3)-adrenergic stimulation) isolated ureters in a concentration-dependent manner. These KUL-7211-induced relaxing effects were antagonized by ICI-118,551 (selective beta(2)-adrenoceptor antagonist, pK(B) value: 8.91 +/- 0.24) in the rabbit ureter and by bupranolol (non-selective beta-adernoceptor antagonist, pK(B) value: 6.85 +/- 0.12) in the canine ureter. KUL-7211 also reduced the spontaneous rhythmic contraction in a canine ureteral spiral preparation in a concentration-dependent manner, the pD(2) value being 6.83 +/- 0.20. These data clearly demonstrate that KUL-7211 selectively stimulates both ureteral beta(2)- and beta(3)-adrenoceptors and potently relaxes ureteral smooth muscle. KUL-7211 may be a novel and useful medication for relieving ureteral colic and promoting stone passage in urolithiasis patients.

Functional characterization of beta-adrenoceptor subtypes in the canine and rat lower urinary tract

PURPOSE

We compared the effect of a beta 3-adrenoceptor (AR) agonist with that of beta 1 and beta 2-AR agonists on the urethra and bladder in the dog and rat.

MATERIALS AND METHODS

In an in vitro experiment we studied the relaxant effect of subtype selective beta-AR agonists in canine and rat urethral and bladder smooth muscle using an organ bath method. In addition, in urethane anesthetized rats we measured urethral pressure and bladder pressure simultaneously in the presence of the beta 3-agonist CL316243 and the beta 2-agonist procaterol in 4 or 5 animals.

RESULTS

In the dog the relaxing effects of isoprenaline in the distal urethra were about half those seen in the detrusor and trigone. The rank order of relaxing potency was CL316243 > dobutamine (beta 1-agonist) = procaterol in detrusor and trigone but procaterol > dobutamine = CL316243 in the prostatic and distal urethra. In rat urethral smooth muscle in vitro the corresponding order was procaterol > CL316243 > dobutamine and the maximal relaxation to each agonist was about half that seen in the bladder. In the anesthetized rat procaterol clearly decreased urethral pressure but CL316243 produced only a slight decrease at its maximal dose, although each agonists clearly reduced bladder pressure. The beta 2-antagonist ICI-118551 counteracted the decrease in urethral and bladder pressure induced by procaterol.

CONCLUSIONS

In rats and dogs a selective beta 3-AR agonist can decrease bladder pressure without affecting urethral pressure.

Norepinephrine inhibits the pelvic pressure increase in response to flow perfusion

PURPOSE

We evaluated the effects of norepinephrine on transport pressures in the normal upper urinary tract of the pig during increasing perfusion rates.

MATERIALS AND METHODS

Anesthetized Danish landrace Yorkshire pigs weighing 38 to 40 kg were studied. Transparenchymally 2, 6Fr catheters were introduced into the left renal pelvis for pressure measurements and perfusion, respectively. An ultrasonic flow probe was inserted around the left renal artery to record blood flow. A 10Fr catheter was placed transurethrally for bladder drainage and the bladder was maintained empty during the entire study. In the 5 group 1 pigs the pelvic pressure increase was examined at increasing perfusion rates of the renal pelvis (2, 4, 6, 8, 10 and 15 ml per minute) in response to endoluminal administration of increasing concentrations of norepinephrine (0, 5, 50 and 100 microg/ml) in saline. In the 5 group 2 pigs the pressure flow study was also done 4 times per animal using isotonic saline.

RESULTS

Endoluminal norepinephrine had a dose dependent effect on the pressure flow relationship. Perfusion with 5 and 50 microg/ml norepinephrine caused a delayed increase and a decrease in pelvic pressure in response to increasing flow rates, whereas perfusion with 100 microg/ml norepinephrine significantly inhibited and almost eliminated the pressure increase at all perfusion rates compared with saline perfusion. Importantly there were no changes in blood pressure, the heart rate or renal arterial blood flow. In group 2 perfusion with isotonic saline resulted in the same pressure response to increasing flow rates each time.

CONCLUSIONS

Endoluminal administration of norepinephrine caused a dose dependent inhibition on the pressure phases of the pressure flow relationship of the upper urinary tract in pigs. No systemic changes were observed. These observations may provide a useful adjuvant treatment strategy for upper urinary tract stone treatment and endoscopy.

Functional and molecular characterization of beta-adrenoceptors in the internal anal sphincter

The purpose of the present study was to characterize different beta-adrenoceptors (beta-ARs) and determine their role in the spontaneously tonic smooth muscle of the internal anal sphincter (IAS). The beta-AR subtypes in the opossum IAS were investigated by functional in vitro, radioligand binding, Western blot, and reverse transcription-polymerase chain reaction (RT-PCR) studies. ZD 7114 [(S)-4-[2-hydroxy-3-phenoxypropylaminoethoxy]-N-(2-methoxyethyl)phenoxyacetamide], a selective beta(3)-AR agonist, caused a potent and concentration-dependent relaxation of the IAS smooth muscle that was antagonized by the beta(3)-AR antagonist SR 59230A [1-(2-ethylphenoxy)-3-[[(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]-(2S)-2-propanol hydrochloride]. Conversely, the IAS smooth muscle relaxation caused by beta(1)- and beta(2)-AR agonists (xamoterol and procaterol, respectively) was selectively antagonized by their respective antagonists CGP 20712 [(+/-)-2-hydroxy-5-[2-[[2-hydroxy-3-[4-[1-methyl-4-(trifluoromethyl)-1H-imidazol-2-yl]phenoxy]propyl]amino]ethoxy]-benzamide methanesulfonate salt] and ICI 118551. Saturation binding of [(125)I]iodocyanopindolol to beta-AR subtypes revealed the presence of a high-affinity site (K(d1) = 96.4 +/- 8.7 pM; B(max1) = 12.5 +/- 0.6 fmol/mg protein) and a low-affinity site (K(d2) = 1.96 +/- 1.7 nM; B(max2) = 58.7 +/- 4.3 fmol/mg protein). Competition binding with selective beta-AR antagonists revealed that the high-affinity site correspond to beta(1)/beta(2)-AR and the low affinity site to beta(3)-AR. Receptor binding data suggest the predominant presence of beta(3)-AR over beta(1)/beta(2)-AR. Western blot studies identified beta(1)-, beta(2)-, and beta(3)-AR subtypes. The presence of beta(1)-, beta(2)-, and beta(3)-ARs was further demonstrated by mRNA analysis using RT-PCR. The studies demonstrate a comprehensive functional and molecular characterization of beta(1)-, beta(2)-, and beta(3)-ARs in IAS smooth muscle. These studies may have important implications in anorectal and other gastrointestinal motility disorders.

Inhibitory effect of beta3-adrenoceptor agonist in lower esophageal sphincter smooth muscle: in vitro studies

We investigated the effects of (R,R)-5-[2-[2-3-chlorophenyl)-2-hydroxyethyl] - amino]propyl] - 1,3 - benzodioxole - 2, 2 - dicarboxylate (CL 316243) (a typical beta3-agonist) on the spontaneously tonic smooth muscle of the lower esophageal sphincter (LES). Studies were carried out in smooth muscle strips and smooth muscle cells (SMCs) of opossum LES. Isometric tension was recorded in the basal state and after CL 316243, and before and after beta3-antagonist (S)-N-[4-[2-[[3-[-(acetamidomethyl)phenoxy]-2-hydroxypropyl]amino]ethyl]phenyl]benzenesulfonamide (L 748337) and nonselective antagonist propranolol. In some experiments, the effects of nonadrenergic noncholinergic (NANC) nerve activation by electrical field stimulation (EFS) were also examined. The effects of CL 316243 were compared with those of nonselective beta-agonist isoproterenol. CL 316243 caused a concentration-dependent relaxation of the LES smooth muscle. The relaxant action of CL 316243 was determined to be directly at the smooth muscle because it remained unmodified by the neurotoxin tetrodotoxin and other neurohumoral antagonists, and also was observed in the SMCs. L 748337 selectively antagonized the relaxant effect of CL 316243 and, conversely, had no significant effect on the inhibitory actions of isoproterenol. CL 316243 (1 x 10(-8) M) caused an augmentation of NANC relaxation in the LES. Another beta3-agonist, (S)-4-[hydroxy-3-phenoxy-propylamino-ethoxy]-N-(2-methoxyethyl)-phenoxyacetamide (ZD 7114), also caused concentration-dependent full relaxation of the LES that was selectively antagonized by beta3-anatagonist 3-(2-ethylphenoxy)-1-[(1S)1,2,3,4-tetrahydronaphth-1-ylaminol]-(2S)-2-propanol oxalate (SR 59230A). These studies defined the effects of characteristic inhibitory beta3-adrenoceptors in the spontaneously tonic LES smooth muscle and suggested a potential therapeutic role in the esophageal motility disorders characterized by hypertensive LES.

Modification of ureteral motility and promotion of urine flow around an intraureteral obstruction by CL-316243, phenylephrine, and furosemide in dogs

The aim of this study was to evaluate the effects of a beta3-adrenoceptor (AR) agonist (CL-316243), an alpha1-AR agonist (phenylephrine), and a loop diuretic (furosemide) on the spontaneous rhythmic contractions of the isolated canine ureter and on an acute ureteral obstruction produced by inflation of a balloon catheter in anesthetized dogs. In the isolated ureter, CL-316243 concentration dependently reduced both the amplitude and frequency of the rhythmic contractions (pD(2): 7.19 +/- 0.33), whereas phenylephrine significantly enhanced both variables (pD(2): 5.26 +/- 0.09) and furosemide reduced them only slightly. In the acute ureteral obstruction model, the intraureteral pressure (IUP) gradually rose to reach a plateau of 58.9 mm Hg after inflation of a balloon catheter within the lower ureter. Intravenous administration of CL-316243 (0.3 microg/kg) significantly reduced the elevated IUP and the resumed urine flow (UF), leading to a sustained reduction in the IUP. In contrast, the IUP continued to increase above the plateau level for 10 minutes after phenylephrine administration (10 microg/kg) and for 30 minutes after furosemide administration (1,000 microg/kg). In the phenylephrine group, the UF resumed when the IUP reached 75.8 mm Hg, and thereafter the IUP gradually decreased in parallel with the increase in the UF. From these results, we conclude that in dogs, CL-316243 reduces the IUP by allowing the UF to resume as a result of a relaxation of ureter at the obstruction site, whereas with phenylephrine, the reduction in the IUP is secondary to a resumption in the UF resulting from an induced contraction of ureter that causes an increase in hydrostatic pressure above the obstruction site.

Characterization of beta-adrenoceptor subtypes in the ferret urinary bladder in vitro and in vivo

In the present study, the beta-adrenoceptor subtypes distributed in the detrusor of the ferret were investigated in functional experiments in vitro and in vivo using a variety of beta-adrenoceptor agonists and antagonists. All the beta-adrenoceptor agonists tested relaxed the isolated detrusor strip, the rank order of potency being (+/-)-(R*, R*)-[4-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]propyl]phenoxy]- acetic acid sodium (BRL 37344A)>(+/-)-4-(3-t-butylamino-2-hydroxypropoxy) benzimidazol-2-one (CGP-12177A), isoprenaline and (R, R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethylamino]propyl]-1, 3-benzodioxole-2,2-dicarboxylate (CL 316,243)>dobutamine and procaterol. In antagonist experiment, 3-(2-allylphenoxy)-1-[(1S)-1,2, 3,4-tetrahydro-naphth-1-ylamino]-(2S)-2-propanol hydrochloride (SR 58894A), but neither 2-hydroxy-5(2-((2-hydroxy-3-(4-((1-methyl-4-trifluoromethyl)1H-imidaz ole-2-yl)-phenoxy)propyl)amino)ethoxy)-benzamide monomethane sulphonate (CGP-20712A) nor erythro-(+/-)-1-(7-methylindan-4-yloxy)-3-isopropylaminob utan-2-ol hydrochloride (ICI-118,551), caused a rightward shift of the concentration-relaxation curve for isoprenaline. In in vivo experiments, isoprenaline and CL 316,243 each reduced bladder pressure in a dose-dependent manner. CL 316,243 was the only drug that did not produce any significant influences on blood pressure and heart rate at doses that reduced bladder pressure. The present functional study provides the first evidence that relaxation of the ferret detrusor by beta-adrenoceptor activation is mediated mainly via the beta(3)-adrenoceptor, as in the human detrusor.

Contribution of beta-adrenoceptor subtypes to relaxation of colon and oesophagus and pacemaker activity of ureter in wildtype and beta(3)-adrenoceptor knockout mice

The smooth muscle relaxant responses to the mixed beta(3)-, putative beta(4)-adrenoceptor agonist, (-)-CGP 12177 in rat colon are partially resistant to blockade by the beta(3)-adrenoceptor antagonist SR59230A suggesting involvement of beta(3)- and putative beta(4)-adrenoceptors. We now investigated the function of the putative beta(4)-adrenoceptor and other beta-adrenoceptor subtypes in the colon, oesophagus and ureter of wildtype (WT) and beta(3)-adrenoceptor knockout (beta(3)KO) mice. (-)-Noradrenaline and (-)-adrenaline relaxed KCl (30 mM)-precontracted colon mostly through beta(1)-and beta(3)-adrenoceptors to a similar extent and to a minor extent through beta(2)-adrenoceptors. In colon from beta(3)KO mice, (-)-noradrenaline was as potent as in WT mice but the effects were mediated entirely through beta(1)-adrenoceptors. (-)-CGP 12177 relaxed colon from beta(3)KO mice with 2 fold greater potency than in WT mice. The maintenance of potency for (-)-noradrenaline and increase for (-)-CGP 12177 indicate compensatory increases in beta(1)- and putative beta(4)-adrenoceptor function in beta(3)KO mice. In oesophagi precontracted with 1 microM carbachol, (-)-noradrenaline caused relaxation mainly through beta(1)-and beta(3)-adrenoceptors. (-)-CGP 12177 (2 microM) relaxed oesophagi from WT by 61.4+/-5.1% and beta(3)KO by 67.3+/-10.1% of the (-)-isoprenaline-evoked relaxation, consistent with mediation through putative beta(4)-adrenoceptors. In ureter, (-)-CGP 12177 (2 microM) reduced pacemaker activity by 31.1+/-2.3% in WT and 31.3+/-7. 5% in beta(3)KO, consistent with mediation through putative beta(4)-adrenoceptors. Relaxation of mouse colon and oesophagus by catecholamines are mediated through beta(1)- and beta(3)-adrenoceptors in WT. The putative beta(4)-adrenoceptor, which presumably is an atypical state of the beta(1)-adrenoceptor, mediates the effects of (-)-CGP 12177 in colon, oesophagus and ureter.

The effects of beta-adrenoceptor agonists on KCl-induced rhythmic contraction in the ureter of guinea pig

In the present study, we tried to determine what effects were induced by beta-adrenoceptor agonists on 40 mM KCl-induced rhythmic contraction and to clarify which beta-adrenoceptor subtypes are involved in the regulation of ureter motility in the guinea pig by using in vitro functional analysis. 40 mM KCl-induced rhythmic contraction was abolished by papaverine (10(-6) M), nicardipine (10(-5) M) and cromakalim (10(-5) M), but was not influenced by atropine (10(-6) M). Isoprenaline decreased the amplitude, and changed the pattern of 40 mM KCl-induced rhythmic contraction in concentration-dependent manner. These results suggest the possibility that the stimulation of beta-adrenoceptors may regulate the ureteral peristalsis. Salbutamol (selective beta2-AR agonist) and CGP12177 (beta(1,2)-AR antagonist and beta3-AR partial agonist) were also effective in decreasing the amplitude and changing the pattern of the rhythmic contraction. The pD2 values of agonists were 7.57 (isoprenaline), 5.80 (CGP12177) and 7.63 (salbutamol), respectively. The concentration-response curves of isoprenaline and salbutamol were rightward shifted by the presence of propranolol, and the apparent pA2 values for propranolol against isoprenaline and salbutamol were 7.12 and 6.29, respectively. These results suggest that inhibition for 40 mM KCl-induced rhythmic contraction of the ureter by isoprenaline and salbutamol mediated mainly via atypical beta-adrenoceptor subtype.