Developmental changes in the biochemical and functional properties of endothelin receptors in rabbit renal pelvis

OBJECTIVE: To examine the effect of age on the biochemical and functional properties, and regional distribution of endothelin (ET) receptors in the rabbit renal pelvis. MATERIALS AND METHODS: The properties of ET receptors in 6-week-old and 6-month-old male rabbit renal pelves were examined using isolated muscle-bath and radioligand receptor-binding techniques. RESULTS: ET-1 caused a significant increase in the contractile force in muscle strips from all regions of the renal pelvis from both age groups, with the following rank order: upper=middle>lower. The magnitude of the ET-1-induced contractile responses were similar in the lower pelvic regions in both ages, but the responses in the upper and middle regions were significantly greater in younger rabbits. ET-1 increased the frequency of spontaneous activity in a concentration-dependent manner in the upper and middle pelvic regions in both age groups, with significantly smaller ED50 values in the younger than in the older rabbits. In both age groups the lower pelvic region lacked spontaneous activity. The density of total ET receptors was higher in the upper and middle regions of the renal pelvis than in the lower renal pelvis of both ages, with the density in the upper and middle regions being greater in older than in younger rabbits. In all regions, ET subtype selective compounds inhibited [125I]ET-1, binding consistent with the predominance of the ETA receptor subtype, except in the lower region of the older rabbits, in which the densities of ETA and ETB subtypes were similar. In all regions, the younger renal pelvis contained a higher proportion of ETA receptors than in older tissues. Light microscopic autoradiographic data indicated the presence of ETA and ETB receptors in smooth muscle and epithelial cells, respectively. CONCLUSION: These data indicate the presence of regional differences in the density of ET receptors and in the contractile responses to ET-1 in rabbit renal pelvis, and that although older rabbit renal pelvis contains more total ET receptors than younger renal pelvis, the latter had a higher portion of the ETA receptor subtype and the younger tissues were more responsive to ET-1.     

Biomechanical and biochemical assessment of properties of the anterior urethra after hypospadias repair in a rabbit model

PURPOSE: We created a rabbit model to test hypospadias operations and investigate the biomechanical properties of the urethra at long-term followup using biomechanical and biochemical assessments. MATERIALS AND METHODS: A total of 38 New Zealand White rabbits were randomized into 4 groups, including controls, sham operation and 2 operation groups (experimental creation of a hypospadias-like defect and acute repair, respectively). In operation group 1 the ventral urethral wall and dorsal plate were longitudinally incised, half of the ventral urethral wall was excised (hypospadias-like defect) and the incised urethra was tubularized (tubularized incised posterior plate urethroplasty group). In operation group 2 the urethra was mobilized from the corpora cavernosa, excised in its distal end (hypospadias-like defect) and advanced to the glanular tip (mobilization and advancement group). At 23 weeks postoperatively biochemical and biomechanical assessments were performed. RESULTS: Maximum urethral strength and stiffness, strain at maximum load and the collagen weight fraction were not significantly different among the groups. Urethral diameter was larger and the total amount of collagen was higher in the mobilization and advancement group only (p <0.05). The mechanical quality of urethral collagen was decreased in the 2 operation groups (p <0.05). CONCLUSIONS: This animal model proved to be useful for testing hypospadias operations and urethral mechanical properties. At long-term followup after experimental hypospadias repair biochemical and biomechanical assessments showed no differences among the groups in mechanical strength, strain and stiffness, and no indication of fibrosis. Consequently testing new hypospadias repair techniques and evaluating their biomechanical long-term results could be performed using hypospadiac animal models before clinical use.     

A pharmacological study of alpha adrenergic receptor subtypes in smooth muscle of human urinary bladder base and prostatic urethra

Postsynaptic alpha adrenergic receptor subtypes mediating contraction of human urinary bladder base and prostatic urethra were investigated in vitro. Alpha adrenergic receptor agonists, noradrenaline and phenylephrine, induced contraction dose-dependently in these tissues. Alpha adrenergic receptor antagonists, prazosin and yohimbine, competitively antagonized the contraction induced by these agonists in the bladder base as well as prostatic urethra. The mean pA2 values for the antagonists in the bladder base and prostatic urethra were as follows: 8.89 and 8.96 for prazosin and 6.30 and 6.45 for yohimbine, respectively. Comparison of pA2 values of prazosin and yohimbine in both the tissues with those values found in the literature for these compounds in a variety of tissues containing alpha-1 or alpha-2 adrenergic receptor indicates that the postsynaptic alpha adrenergic receptor subtype in the human urinary bladder base and prostatic urethra is the alpha-1 type, not the alpha-2 type.     

Muscarinic receptor subtypes in human and rabbit bladder

Subtypes of muscarinic receptors have been proposed by several investigators, based on differences in the potency of muscarinic agonists in various tissues. Development of selective muscarinic agonists and antagonists for the urinary bladder would be extremely useful since side effects of the presently used drugs often limit their clinical usefulness. Direct investigation of muscarinic receptor subtypes by radioligand binding techniques has recently become possible. The muscarinic antagonist pirenzepine distinguishes between a high affinity and low affinity binding site in several tissues. Results of the present investigation indicate that only the low affinity pirenzepine binding site is present in both human and rabbit bladder. Muscarinic receptor linked biochemical responses (increased phosphatidyl inositol turnover and inhibition of adenyl cyclase) were also consistent with the presence of only the low affinity pirenzepine binding receptor subtype in both human and rabbit bladder.     

Two cases of ectopic prostatic tissue in the prostatic urethra

Two cases of ectopic prostatic tissue or adenomatous polyps with prostatic type epithelium in the prostatic urethra were reported. They were 30-and 33-year-old males suffering from gross-hematuria and from urethral pain on urination with terminal gross-hematuria. Endoscopic examination revealed papillary lesions from the dilated orifice of the prostatic utricle. Biopsied pathology demonstrated a tissue similar to that of the prostatic gland. PSA (prostatic specific antigen) stain using immunohistochemical methods was positive. Histogenesis and the importance of this lesion particularly as a cause of hematuria in the young male adult were discussed.     

Papillary adenoma of the prostatic urethra

Six patients with papillary adenoma of the prostatic urethra are described. Their ages ranged from 39 to 70 years old. Two of them showed evidence of clinical recurrence 1 year after treatment. The pathological features as well as the immunohistochemical demonstration of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) are illustrated. A brief review of the literature is discussed with special emphasis on the histogenesis and nature of this lesion.     

Regional differences in sensory innervation and suburothelial interstitial cells in the bladder neck and urethra

OBJECTIVE

To identify and characterize possible structural specialisations in the wall of the lower urinary tract (LUT) in the region of the bladder urethral junction (BUJ), with the specific objective of identifying regional variations in sensory nerve fibres and interstitial cells (ICs).

MATERIALS AND METHODS

The bladder base and urethra was removed from five male guinea pigs killed by cervical dislocation. Tissue pieces were incubated in Krebs’ solution at 36 °C, gassed with 95% O₂ and 5% CO₂, fixed in 4% paraformaldehyde and processed for immunohistochemistry. The nonspecific marker vimentin and the general neuronal marker protein gene product (PGP) 9.5 were used to identify ICs and nerve fibres, respectively. Specific antibody binding was visualized using the appropriate secondary antibodies.

RESULTS

The wall of the LUT in the region immediately between the bladder base and the urethra, the BUJ, differed in its cellular composition relative to the adjacent areas. PGP‐positive (PGP⁺) nerve fibres, presumptive afferent fibres, lay within the urothelium running between the epithelial cells. There were two general nerve patterns: branching fibres with no varicosities, and complex fibres with varicosities. Fibre collaterals with varicosities exited the urothelium and occupied the space under the urothelium adjacent to the layer of suburothelial ICs. The latter, lamina propria and around the muscle bundles were identified using vimentin (vim⁺). In the base a few vim⁺ cells were also PGP⁺. In the region of the BUJ there was a decrease in the amount of smooth muscle. In this region, below the lamina propria, there was an area densely populated with vim⁺/PGP⁺ ICs. Nerve fibres ran between the cells in this region.

CONCLUSION

These structural specialisations within the urothelium and deeper layers of the BUJ suggest that they might be associated with specific functions. The localized highly branched network of the putative afferent nerves suggests the presence of a local axonal reflexes involving possible cross‐talk between the urothelium and suburothelial layer. The function of the specialized region of ICs is not known and must await further information on the functional properties of this novel cell type. These observations show further the cellular heterogeneity of the cells in the LUT and the complexity of the structures. One of the major current challenges in functional urology is to understand the relationships between these novel structures and overall bladder and urethral function.     

Somatostatin receptor subtypes in hormone-refractory （castration-resistant） prostatic carcinoma

The aim of this study was to examine the tissue expression and localisation of the somatostatin receptors (SSTRs) in hormone-refractory (HR) prostate cancer (PCa). Five SSTRs were evaluated immunohistochemically in 20 radical prostatectomies (RPs) with Gleason score (GS) 3+3=6 PCa, in 20 RPs with GS 4+4=8 and 4+5=9 PCa, and 20 transurethral resection of the prostate specimens with HR PCa. The mean values in the cytoplasm (all five SSTRs were expressed), membrane (only SSTR3 and SSTR4 were expressed) and nuclei (only SSTR4 and SSTR5 were expressed) of the glands in HR PCa were 20-70% lower than in the other two groups, the differences being statistically significant. All five SSTRs were expressed in the smooth muscle and endothelial cells of HR PCa, the mean values being lower than in the other two groups. In conclusion, this study expands our knowledge on the expression and localisation of five SSTRs in the various tissue components in the HR PCa compared with hormone-sensitive PCa.     

Inverted papillomas of the prostatic urethra

Inverted papillomas of the genitourinary tract are uncommon benign neoplasms usually occurring in the urinary bladder and less frequently in the upper urinary tract. To date, there are scant data and no comprehensive studies of inverted papilloma originating in the prostatic urethra. We identified 21 cases and evaluated their demographic, clinical, and histopathologic features. Patients had a mean age of 65.1 years (range: 30 to 89 y), with 10/21 (47.6%) presenting with gross hematuria (n = 8) or irritative symptoms (n = 2) related to the inverted papilloma and 11/21 (52.4%) detected incidentally during work-up/treatment of prostate cancer (n = 6) or benign prostatic hypertrophy (BPH) (n = 5). Fourteen cystoscopically evaluated lesions measured 0.1 to 2.0 cm, and were described as polypoid (n = 9), papillary (n = 4), or an enlarged median lobe (n = 1). Lesions were diagnosed on transurethral resection (n = 8), biopsy/polypectomy targeted to the lesion (n = 6), radical prostatectomy for prostate cancer (n = 4), or biopsy unrelated to the lesion (n = 3). Histologically, 14/21 cases (67%) displayed classic inverted papilloma architecture. The remaining cases showed foci of squamous metaplasia with moderate atypia (n = 4), rare true papillary fronds in a classic inverted papilloma background (n = 2), or both (n = 1). Eleven cases with prostatic tissue revealed adenocarcinoma of the prostate [n = 6; Gleason score 6 (n = 3) or 7 (n = 3)], high-grade prostatic intraepithelial neoplasia (n = 1), benign prostatic hypertrophy (n = 3), or adenosis (n = 1). No patients had a prior history of either inverted papilloma or urothelial carcinoma, whereas 2 patients were diagnosed with high-grade urothelial carcinoma of the bladder synchronous with their inverted papilloma diagnosis. Only 1 of the 18 patients with available follow-up had a recurrence of inverted papilloma in the prostatic urethra. None of the other patients had local recurrences or recurrences at other locations in the urinary tract (mean follow-up 39.9 mo; range: 3 to 120 mo). Inverted papillomas of the prostatic urethra are benign lesions that are commonly detected incidentally and are not associated with a history of urothelial malignancy. Although urothelial carcinoma elsewhere in the genitourinary tract may occur simultaneously, malignant transformation or recurrence as a malignant lesion has not been identified in inverted papilloma of the prostatic urethra.     

Villous adenoma of the prostatic urethra

We present a case of villous adenoma of the prostatic urethra, without malignant transformation. A review of the diagnostic and therapeutic criteria and pathogenic hypotheses on this kind of lesion in the lower urinary tract are made.     

Papillary adenoma of the prostatic urethra

Acquired polyps of the male urethra often present with hematuria and sometimes hemospermia. The histogenesis of these tumors has been debated. We report a case of a prostatic urethral polyp that proved to be of prostatic epithelial differentiation, as demonstrated by immunohistochemical identification of prostatic acid phosphatase and prostatic specific antigen within the tumor cells.     

Inverted papilloma of the prostatic urethra

The inverted papilloma is a rare urothelial tumor, and its localization at the prosthatic urethra is also exceptional. We present a case of inverted papilloma of the prostatic urethra in a 72 years-old male, with symptoms of urinary flow obstruction. The diagnose is obtained after urethrocistoscopy and transurethral resection at the same time. We discuss about the etiology, clinical presentation, diagnose and treatment of this rare tumor, making special attention to its malignancy ability.     

Papillary adenocarcinoma of the prostatic urethra

Three cases of papillary carcinoma of the prostate (also called endometrial adenocarcinoma of the prostate; endometrioid carcinoma) were studied for prostate-specific antigen in order to determine their origin and histogenesis. All 3 cases were prostate-specific antigen positive. Two patients were treated with hormonal therapy, 1 with radiotherapy.     

Endothelin in the urinary bladder. II. Characterization of endothelin receptor subtypes.

Endothelins (ET-1, ET-2, ET-3) are a family of regulatory peptides with diverse biological functions, including modulation of smooth muscle tone. To evaluate the possible role of endothelins in the control of the detrusor smooth muscle of urinary bladder, we have investigated the responses of isolated strips of bladder dome and base to endothelins, in organ chambers, and characterized the receptors for these isopeptides in bladder membranes. ET-1, ET-2 and to a lesser extent ET-3 caused sustained concentration-dependent contraction of bladder dome and base. The contraction to endothelins, unlike the short-lived contraction produced by cholinergic agents, was long lasting and difficult to wash out. Equilibrium binding studies demonstrated that endothelin isoforms bound to bladder membrane receptors specifically, with high affinity (KD of 0.4-0.6 nM) and limited capacity (60-420 fmol/mg protein). Competition analysis showed two populations of receptors: one with high affinity for ET-1 and ET-2 and low affinity for ET-3 and another with high affinity for ET-1, ET-2 and ET-3. Chemical affinity labeling of endothelins to bladder membranes demonstrated that ET-1 and ET-2 were cross-linked to three proteins (75, 52 and 34 kDa, respectively), whereas ET-3 was cross-linked mainly to a 34 kDa protein. The data obtained from equilibrium binding studies, competition analysis and cross-linking experiments suggest that at least two endothelin receptor subtypes exist in bladder tissue. These observations further suggest that bladder smooth muscle tone may be modulated by endothelin or an endothelin-like substance via interaction with specific receptor sites.