Accuracy of free thyroxine measurements across natural ranges of thyroxine binding to serum proteins

Systemic inaccuracies, proportional to the concentrations of serum proteins and the thyroxine (T4) they carry, have been reported in direct free T4 immunoassays. However, analytical recoveries of free T4 have not been carefully examined in most current methods, and they have not previously been examined across the pathophysiological range of serum T4 binding. In the present study we investigated ranges of serum T4 binding using free and total T4 measurements from 1359 individuals. Carefully characterized, gravimetrically calibrated, serum-based free T4 test solutions were then prepared with a constant normal free T4 concentration (12 ng/L) and varied serum T4 binding (approximately 300:1 to 24,000:1, ng protein bound T4: ng free T4). These standardized test solutions were analyzed using five T4 analog based free T4 methods. Analytical recoveries were calculated as ratios of actual free T4 measurements to the target value, and expressed as a percent of the target. Analytical recoveries were directly proportional to the extent of serum T4 binding and ranged 2% to 155%, 25% to 131%, 53% to 106%, 37% to 93%, and 37% to 73%, lowest to highest, in different methods. These systemic inaccuracies will confound interpretations of free T4 test results in clinical conditions with altered T4 binding. Future investigations into free T4 status must examine the analytical recovery of the free T4 method(s) used, as they relate to the extent of serum T4 binding in the clinical condition(s) studied.

Developmental aspects of endothelin receptors in rabbit lower urinary tract

Since evidence of development/age-related alterations of endothelin receptors in circulation and respiration systems has been increasing, we attempted to investigate the pharmacological characterization of endothelin receptors in neonatal, premature, and mature male rabbit lower urinary tract. The biochemical properties of ET receptors were examined in the lower urinary tracts of 1-day (neonatal)-, 6-week (premature)-, and 1-year(mature)-old male rabbits with binding technique utilizing [(125)I]ET-1. The rank orders of the densities (B(max) values) of endothelin receptors in the bladder dome, bladder base, and urethra of different aged rabbits were bladder dome, 1 day > 6 week &vbar;Ls 1 year, bladder base, 1 day > 6 week &vbar;Ls 1 year, and urethra, 1 day > 6 week > 1 year. The pharmacological profiles of these binding sites inhibited by various kinds of endothelin receptor compounds showed similar K(i) values and similar proportions of endothelin receptor subtypes in the same regions of 1-day-, 6-week-, and 1-year-old animals. Our data clearly demonstrated the presence of regional difference and development-related changes in the density and subtype specificity of endothelin receptors in the lower urinary tract of the male rabbit. Neurourol. Urodynam. 19:71-85, 2000.

The tert-butylammonium perchlorate complex of 2,3-naphtho-18-crown-6 at 115 K

In the title complex, tert-butylammonium perchlorate-2,5,8,11,14,17-hexaoxatricyclo[16.8.0.0(20,25]hexac osa- 1(26),18,20(25),21,23-pentaene-ethyl acetate-dichloromethane (4/4/1/1), C4H12N+.C20H26O6.ClO4-.0.25C4-H8O2.0.25CH2Cl2 , the tert-butylammonium cation binds to the macrocyclic host (Chemical Abstracts name: 2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-hexaoxanaphtho [2,3- b]cyclooctadecin) in the expected tripod arrangement, while the perchlorate anion links naphthyl groups in the crystal through C-H...O-Cl-O...H-C interactions. Thermal motion analysis indicates that the tert-butylammonium group and the perchlorate anion each librate with respect to the host, with amplitudes of 6.2 (4) and 11.4 (2) degrees, respectively.

Disruption of the sarcoglycan-sarcospan complex in vascular smooth muscle: a novel mechanism for cardiomyopathy and muscular dystrophy

To investigate mechanisms in the pathogenesis of cardiomyopathy associated with mutations of the dystrophin-glycoprotein complex, we analyzed genetically engineered mice deficient for either alpha-sarcoglycan (Sgca) or delta-sarcoglycan (Sgcd). We found that only Sgcd null mice developed cardiomyopathy with focal areas of necrosis as the histological hallmark in cardiac and skeletal muscle. Absence of the sarcoglycan-sarcospan (SG-SSPN) complex in skeletal and cardiac membranes was observed in both animal models. Loss of vascular smooth muscle SG-SSPN complex was only detected in Sgcd null mice and associated with irregularities of the coronary vasculature. Administration of a vascular smooth muscle relaxant prevented onset of myocardial necrosis. Our data indicate that disruption of the SG-SSPN complex in vascular smooth muscle perturbs vascular function, which initiates cardiomyopathy and exacerbates muscular dystrophy.

Effects of insulin treatment on diabetes-induced alterations in endothelin receptors in rat ureter

BACKGROUND

The present investigation was undertaken to examine the effect of insulin treatment on diabetes-induced alterations in endothelin (ET) receptors in rat ureters.

METHODS

The biochemical properties of ET receptors were examined in rat ureters from the following groups: 8 weeks diabetic (D8); 8 weeks age-matched control (C8); 16 weeks diabetic (D16); 16 weeks diabetic-insulin treated (insulin started 8 weeks after the onset of diabetes) (DI16); and 16 weeks age-matched control (C16). Diabetes was induced by the i.v. injection of 65 mg/kg streptozotocin (STZ).

RESULTS

The densities of ET receptors (Bmax values), as determined by saturation experiments with [125I]-ET-1, in the ureteral plasma membranes of D8, C8, D16, DI16 and C16 were 91.7 +/- 10.1, 42.1 +/- 7.2, 71.1 +/- 2.4, 51.5 +/- 6.3 and 45.1 +/- 3.3 fmol/mg of protein, respectively. [125I]-ET-1 binding to the ET receptors in rat ureteral membrane particulates was inhibited by ET-1 (non-selective), ET-3 (ET(B/C selective), BQ610 (ET(A) selective) and IRL 1620 (ET(B) selective) with the following rank order of Ki values: ET-1 < BQ 610 < ET-3 << IRL 1620. The pharmacological profile of the ET receptors was similar in all groups examined and was consistent with the predominance of the ET(A) receptor subtype in the ureteral membrane particulates. The subtype specificity of ET receptors in the ureteral tissues is confirmed with inhibition data obtained from similar binding studies in cloned human ET(A) and ET(B) receptors.

CONCLUSION

The data indicate that diabetes results in an up-regulation of ET receptors in the rat ureter, which is normalized by insulin treatment.

Inducible nitric oxide synthase with transitional cell carcinoma of the bladder

PURPOSE

Nitric oxide (NO) plays a critical role as both a cell signaling molecule and as a cytotoxic/cytostatic mediator. Nitric oxide synthase (NOS) present in macrophages and neutrophils produces NO in response to immune stimulation. We evaluated NO production in both bladder tissue and urine from patients with transitional cell carcinoma (TCC) of the bladder.

MATERIALS AND METHODS

Inducible NOS (iNOS) RNA and protein were evaluated in bladder tissue from patients with and without TCC. Human iNOS-RNA products were identified with the reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis using a polyclonal antibody directed against iNOS recognized immunoreactive iNOS protein. Using the same iNOS antibody, the distribution of iNOS was examined in formalin-fixed, paraffin embedded samples of various grades of TCC. NOS activity was measured in the urine particulate fraction from patients with TCC and from controls by the conversion of [14C]-L-arginine to [14C]-L-citrulline.

RESULTS

Inducible NOS-RNA products and iNOS specific proteins were found in bladder tissue that contained TCC but not in control bladder tissue. Inducible NOS was uniformly localized in inflammatory cells within the carcinomas. Scattered tumor cells expressed iNOS in 8 of 12 specimens. There was no clear relationship between tumor immunoreactivity and tumor grade. NOS activity in urine from patients with TCC was not significantly elevated or decreased in comparison with control urine.

CONCLUSIONS

Inducible NOS is expressed by cells comprising and surrounding human bladder tumors. It is primarily localized to inflammatory cells, but also is demonstrated within individual tumor cells.

A randomized double-blind trial of oral L-arginine for treatment of interstitial cystitis

PURPOSE

Nitric oxide synthase activity is decreased in the urine of patients with interstitial cystitis compared to the urine of controls. In a preliminary trial oral L-arginine, the substrate for nitric oxide synthase, increased urinary nitric oxide synthase activity and improved interstitial cystitis symptoms. This randomized, double-blind, placebo controlled study further investigates the efficacy of L-arginine treatment for interstitial cystitis.

MATERIALS AND METHODS

A total of 53 interstitial cystitis patients were assigned to receive daily 1,500 mg. L-arginine or placebo orally for 3 months. Interstitial cystitis symptoms were assessed by interviews at 2 weeks, and 1, 2 and 3 months.

RESULTS

The trial was completed by 21 of 27 patients in the L-arginine group and 25 of 26 in the placebo group. Using per protocol analysis 29% (6 of 21 patients) in the L-arginine group and 8% (2 of 25) in the placebo group were clinically improved by the end of the trial (p = 0.07). A Likert scale showed greater global improvement in the L-arginine group (48%, 10 of 21) compared to the placebo group (24%, 6 of 25) at 3 months (p = 0.05) with a decrease in pain intensity (p = 0.04), and tendency toward improvement in urgency (p = 0.06) and frequency of pain (p = 0.09). Using an intention to treat approach to analysis there were no differences between groups.

CONCLUSIONS

Oral L-arginine (1,500 mg. daily) may decrease pain and urgency in a subset of interstitial cystitis patients.

Detection of urinary tract infections by reduction of nitroblue tetrazolium

BACKGROUND

Nitroblue tetrazolium (NBT) reduction to formazan has been used as a marker for nitric oxide synthase (NOS). Since inducible NOS activity is elevated in urine from patients with urinary tract infections (UTIs), we investigated the accuracy of NBT reduction as an early predictor of UTIs and quantified the relationship between inducible NOS and NBT.

METHODS

Urine samples from 434 patients were screened for the presence of UTIs with leukocyte-esterase and nitrite dipsticks and with NBT reduction. The rapid screening results from each test were compared to urine culture results. In addition, NBT reduction parameters were measured in urine pellet at 595 nm after incubation with one of four factors: NOS cofactors, NOS inhibitors, NADH, or superoxide dismutase/catalase.

RESULTS

As a urine screening test for UTIs, NBT reduction was more sensitive with a higher negative predictive accuracy than the nitrite dipstick. NBT reduction also was more specific with a higher positive predictive accuracy and negative predictive accuracy than the leukocyte-esterase dipstick. In infected urine pellet, both NADPH, a NOS cofactor, and NADH increased NBT reduction. Superoxide dismutase/catalase decreased NBT reduction.

CONCLUSIONS

Although NOS may not be the only NBT reducing enzyme, rapid, visible reduction of NBT is induced in urine from patients with UTIs.

Characterization, localization and distribution of alpha1 adrenoceptor subtype in male rabbit urethra

PURPOSE

The subtype specificity, localization and distribution of urethral alpha1-adrenoceptors were studied in the male rabbit urethra.

MATERIALS AND METHODS

The properties of the urethral alpha1-adrenoceptors were investigated using radioligand receptor binding and light microscopic autoradiography with [125I]iodo-2-[b-(4-hydroxyphenyl)-ethylaminomethyl]tetralone (HEAT), and immunohistochemistry with monoclonal anti-alpha smooth muscle actin and anti-alpha sarcomeric actin antibodies.

RESULTS

Saturation experiments with [125I]HEAT demonstrated the presence of significant amounts of a single high affinity binding site for alpha1 adrenoceptors in the male rabbit urethra. The pharmacological profile of the alpha1 adrenoceptors in rabbit urethra, determined by inhibition experiments with subtype selective alpha1 adrenoceptor antagonists, was characterized by the following rank order of potency of inhibition constants (Ki values): prazosin < or = WB 4101 < spiperone < 5-methylurapidil < BMY 7378. The pKi values for the rabbit urethra were correlated with the pKi values for rat spleen, submaxillary glands, and vas deferens and for those reported for cloned alpha1d receptors with correlation coefficients of 0.68, 0.929, 0.909, and 0.523, respectively.

CONCLUSIONS

The pharmacological characterization demonstrates the predominance of alpha1A or alpha1A + alpha1B adrenoceptor subtype(s) in male rabbit urethral smooth muscle. Furthermore, the autoradiographic and immunohistochemical studies show a heterogeneous distribution of alpha1 adrenoceptors along the longitudinal axis of the urethra, within the smooth muscle fibers, with the receptors being localized more densely in the proximal than in the distal urethra.

Endoscopic management of complete obstruction of a ureteroneocystostomy in an infant

We present the case of an 18-month-old female who, after bilateral ureteroneocystostomies, developed complete obstruction at the left ureteroneocystostomy site. Using endourologic techniques, patency of the ureteroneocystostomy was re-established and has remained unobstructed during her 4-year follow-up.

Bladder instillation and intraperitoneal injection of Escherichia coli lipopolysaccharide up-regulate cytokines and iNOS in rat urinary bladder

Systemic bacterial lipopolysaccharides (LPS) induce inflammatory responses characteristic of sepsis. Instillation of LPS into rat bladder produces a localized inflammatory response similar to that seen in urinary tract infections (UTIs). Four hours after intravesical instillation of LPS, neutrophils infiltrate into the bladder, and mRNA for inducible nitric oxide synthase (iNOS) and the cytokines, interleukin (IL)-6 and IL-10, is detected in rat bladder but not in the kidney. Induction of iNOS protein is inferred because urinary nitrate and cGMP levels are increased 4 hr after LPS intravesical instillation and remain elevated for at least 24 hr. When LPS is injected intraperitoneally, iNOS and IL-6 mRNA are induced both in the bladder and in the kidney. These data are consistent with the effects of intravesical instillation of LPS remaining localized, iNOS activity increases in both particulate and soluble bladder fractions when measured 4 hr after intravesical instillation of LPS. The magnitude of these increases in iNOS activity in the bladder is not as great as when LPS is injected intraperitoneally. Intravesical instillation of LPS induces no increase in lung or kidney NOS activity. The localized inflammatory response produced by intravesical instillation of LPS demonstrates the importance of LPS as a mediator of the host response in UTIs and supports the use of urinary measurements of nitrate and cGMP in humans as indicative of the localized induction of iNOS in UTIs.

A novel bioassay for P-glycoprotein functionality using cytochalasin D

The functional contribution of both P-glycoprotein (P-gp) and the multidrug resistance-associated protein (MRP) to multidrug resistance (MDR) in tumor cells is commonly determined by drug cytotoxicity and/or accumulation/efflux tests. We report on a bioassay developed for the specific detection of functional P-gp levels and the efficacy of related chemosensitizers (CD-P-gp-assay). The assay is based on the flow cytometric measurement of changes in the > or = G2M cell cycle compartment which are due to the induction of polykaryons after exposure of proliferating cells to three defined cytochalasin D (CD) concentrations with and without verapamil. As demonstrated in 13 well-characterized MDR cell models (20 resistant sublines), there is a significant correlation between cytokinesis-blocking CD doses, as well as responsiveness to chemosensitizers and MDR1 gene expression (mRNA and P-gp) allowing discrimination between different levels of P-gp-MDR. CD-P-gp-assay specificity was assessed by testing 23 compounds: 19 known as potent inhibitors of P-gp-MDR, some of them, though to a lesser extent, also of MRP-MDR; 1 inhibiting MRP-but not P-gp-MDR; 3 inactive in both types of MDR. A modulation of CD activity was confined exclusively to both P-gp-expressing cell lines and P-gp chemosensitizers. CD cytoskeletal activity measured by FACS is a specific and sensitive tool with which to detect functional P-gp and related chemosensitizers.

Effect of long-term oral L-arginine on the nitric oxide synthase pathway in the urine from patients with interstitial cystitis

PURPOSE

We attempted to determine whether oral L-arginine, the substrate for nitric oxide synthase, increases nitric oxide synthase activity and cyclic guanosine monophosphate (cGMP) levels in the urine from interstitial cystitis patients. Nitric oxide and cGMP are decreased in urine from interstitial cystitis patients and both induce smooth muscle relaxation and immunological responses. Increasing urinary nitric oxide and cGMP may ameliorate interstitial cystitis symptoms.

MATERIALS AND METHODS

Eight patients with interstitial cystitis were given L-arginine (1,500 mg. a day) orally for 6 months. Before and during treatment nitric oxide synthase activity and inducible nitric oxide synthase protein, cGMP, nitrate plus nitrite and interleukin 8 (IL-8) levels were measured in urine.

RESULTS

After 2 weeks to 1 month of oral L-arginine treatment, urinary levels of nitric oxide synthase related enzymes and products increased significantly, while levels of the cytokine IL-8 were not changed significantly. IL-8 was significantly elevated in interstitial cystitis patients with leukocyte esterase positive urine.

CONCLUSIONS

Long-term oral administration of L-arginine increases nitric oxide related enzymes and metabolites in the urine of patients with interstitial cystitis, which is associated with a decrease in interstitial cystitis related symptoms.

Muscarinic receptor subtypes and receptor-coupled phosphatidylinositol hydrolysis in rat bladder smooth muscle

BACKGROUND

The purpose of this study was to evaluate the muscarinic receptor subtypes expressed in rat bladder smooth muscle and characterize the muscarinic receptor-coupled phosphatidylinositol (PI) hydrolysis in order to clarify the first step of bladder smooth muscle contraction.

METHODS

Expressions of mRNAs of muscarinic receptor subtypes were examined by Northern blot analysis. Changes in the mass of inositol 1,4,5-trisphosphate (IP3) and the inhibitory effects of muscarinic subtype specific antagonists on PI hydrolysis were determined after carbachol stimulation.

RESULTS

mRNAs of m2 and m3 genes, encoding M2 and M3 receptors, were expressed in rat bladder smooth muscle. Carbachol produced a rapid increase of IP3, which returned to the basal level within 30 seconds. 4-Diphenylacetoxyl-N-methylpiperidine methiodide (4-DAMP; M1 and M3 antagonist) strongly inhibited the PI hydrolysis, but methoctramine (M2 antagonist) partially inhibited it at 10(-4) mol/L. The IC50 value for atropine was 9.5 x 10(-9) mol/L, for pirenzepine 6.4 x 10(-6) mol/L, and for 4-DAMP 1.5 x 10(-7) mol/L.

CONCLUSION

M2 and M3 receptors are expressed in rat urinary bladder. Only M3 receptor was involved in the production of IP3, which might induce the initial phase of contractile response in rat bladder smooth muscle after carbachol stimulation.

Pseudoexstrophy of the bladder: case report and literature review

The authors present a case of a boy newborn who had bladder pseudoexstrophy and multiple congenital anomalies. In addition to this unusual variant of the exstrophy-epispadias complex, the patient was found to have a posterior cleft palate, an omphalocele, and an imperforate anus.

Improvement in interstitial cystitis symptom scores during treatment with oral L-arginine

PURPOSE

Urinary nitric oxide synthase activity is decreased in patients with interstitial cystitis. Since nitric oxide may be an important determinant of the symptoms and immunological responses associated with interstitial cystitis, patients with this disease were treated with oral L-arginine, the substrate for nitric oxide synthase.

MATERIALS AND METHODS

Ten patients took 1.5 gm. L-arginine orally daily for 6 months. Interstitial cystitis symptoms were surveyed before and during the 6-month trial.

RESULTS

Oral L-arginine treatment resulted in a significant decrease in urinary voiding discomfort, lower abdominal pain and vaginal/urethral pain. Urinary frequency during the day and night also significantly decreased.

CONCLUSIONS

This self-controlled study provides evidence that long-term oral L-arginine improves interstitial cystitis related symptoms.

The ultrasonographic differentiation of obstructive versus nonobstructive hydronephrosis in children: a multivariate scoring system

PURPOSE

We identified sonographic prognosticators to aid in distinguishing obstructive from nonobstructive hydronephrosis in children.

MATERIALS AND METHODS

Twelve sonographic variables were initially analyzed to determine significant associations between the variables and the presence of urinary tract obstruction as defined by diuretic radionuclide renography. The significant findings were subsequently subjected to logistic regression models to identify potential predictors for obstructive hydronephrosis.

RESULTS

The 7 variables associated with a significantly higher risk of urinary tract obstruction were increased echogenicity, parenchymal rims 5 mm. or less, contralateral hypertrophy, resistive index ratio 1.10 or greater, resistive index difference with diuresis of 70% or greater, ureter diameter 10 mm. or greater and aperistaltic ureter. These variables were used for the development of a multivariate scoring system.

CONCLUSIONS

The obstructive scoring system shows promise as a screening method for the sonographic differentiation of obstructive from nonobstructive hydronephrosis in children.

Age-dependent changes in particulate and soluble guanylyl cyclase activities in urinary tract smooth muscle

Regional and age specific differences are observed in the sodium nitroprusside induced relaxation responses in the urinary tract. To clarify these differences, guanylyl cyclase activity is assayed in particulate and soluble fractions from the ureter, bladder dome, and urethra of young (11-18 days), adult (90-100 days), and old adult (2-3 years) guinea pigs. The rank order of soluble guanylyl cyclase activities is urethra = ureter > bladder dome with the largest decreases with aging occurring in the bladder. Atrial natriuretic factor (10(7) M) increases particulate guanylyl cyclase activity in the three tissues at all ages tested, with the activity being highest in the ureter. ATP (0.5 mM) activates particulate guanylyl cyclase in the ureter, bladder and urethra of old adult guinea pigs, and enhances atrial natriuretic factor induced activation of particulate guanylyl cyclase in all tissues and at all ages tested. The higher levels of soluble guanylyl cyclase activity in the urethra and ureter compared to the bladder parallel sodium nitroprusside induced relaxation in these tissues.

Ipsilateral pyeloureterostomy for managing lower pole reflux with associated ureteropelvic junction obstruction in duplex systems

PURPOSE

In duplex renal systems with a normal upper pole collecting system, and a lower pole collecting system with reflux and ureteropelvic junction obstruction or a kink at the ureteropelvic junction (that is reflux with trapping), treatment must address reflux and obstruction. We reviewed the results of ipsilateral pyeloureterostomy as a single corrective procedure.

MATERIALS AND METHODS

We retrospectively reviewed our experience with 10 children who had complete ureteral duplication with lower pole reflux (grades III to V) and associated lower pole ureteropelvic junction obstruction or a ureteral kink with trapping. All patients were treated with ipsilateral end-to-side pyeloureterostomy. Followup ranged from 1 to 14 years.

RESULTS

All patients had a good postoperative result, there have been no immediate or long-term complications and no subsequent surgical procedure was needed. All patients had continued lower pole renal growth with good function, 9 had resolution or a marked decrease in pelvicaliceal dilatation and none had evidence of obstruction.

CONCLUSIONS

Ipsilateral end-to-side pyeloureterostomy for treating reflux into the lower moiety of a duplicated collecting system with associated ureteropelvic junction obstruction or a kink appears to be a single, safe corrective procedure that simultaneously manages vesicoureteral reflux and relieves the proximal obstructive process.

Laparoscopic evaluation and management of a child with ambiguous genitalia, ectopic spleen, and Meckel's diverticulum

Laparoscopy may be helpful in the evaluation and management of the child with intersex. Laparoscopic excision of dysgenetic gonads may be necessary due to the increased risk of malignancy. Residual müllerian duct structures are removed to prevent symptomatic complications at puberty. We present the case of a laparoscopic evaluation and management of a 46XY child with ambiguous genitalia, as well as the laparoscopic management of two unrelated anomalies discovered at the time of surgery.

Neurokinin induced inositol phosphate production in guinea pig bladder

PURPOSE

To examine second messenger pathways involved in neurokinin induced bladder contractions.

MATERIALS AND METHODS

Neurokinin induced changes in inositol phosphate production and in adenylyl cyclase activity are measured in the guinea pig bladder.

RESULTS

Substance P, substance P methyl ester, neurokinin A, and neurokinin B each increase [3H]-inositol phosphate production in the guinea pig bladder. Substance P (10(-6) M) increases [3H]-inositol trisphosphate levels within 30 sec. Substance P and neurokinin A have an additive effect on inositol phosphate production, however substance P (10(-5) M) or neurokinin A (10(-5) M) induced inositol phosphate production is less than that induced by carbachol (10(-5) M). Neurokinin B and to a lesser extent neurokinin A inhibit forskolin-activated adenylyl cyclase activity.

CONCLUSIONS

These data are compatible with neurokinin-induced inositol phosphate production being coupled to increases in contractile force of the guinea pig urinary bladder, however more than one second messenger pathway may be involved.

Evidence for the presence of regional differences in the subtype specificity of muscarinic receptors in rabbit lower urinary tract

To elucidate the subtype specificity of muscarinic cholinergic receptors in mediating contractile responses in the lower urinary tract, we investigated contractile and biochemical properties of muscarinic receptors in bladder dome, bladder base and urethra of the rabbit. Isometric contractile response curves to increasing concentrations of carbachol were constructed in the absence and presence of various concentrations of subtype selective muscarinic antagonists. Bladder dome, bladder base, and urethra demonstrate different characteristics in terms of efficacy and potency with respect to carbachol-induced contractile responses. Emax values are significantly larger and ED50 values are significantly smaller in bladder dome and bladder base than in urethra. Calculation of the pA2 values, the negative logarithm of the antagonist affinity constant (KB), for a series of muscarinic antagonists, i.e., atropine (nonselective), pirenzepine (M1 selective), methoctramine (M2 selective), and 4-DAMP (M1/M3 selective) indicate that the carbachol-induced contractile response in bladder dome and bladder base is mediated through the M3 receptor subtype whereas the carbachol-induced contractile response in urethra is probably mediated through the M1 and/or M3 and possibly M2 subtypes. Muscarinic cholinergic antagonists inhibit [3H]quinulidinyl benzilate binding to bladder dome, bladder base and urethra with the following rank order of affinities: atropine > 4-DAMP > methoctramine > pirenzepine. The binding data indicate the predominance of the M2 receptor subtype in all three regions.