Interactive virtual 3D models of renal cancer patient anatomies alter partial nephrectomy surgical planning decisions and increase surgeon confidence compared to volume-rendered images

Purpose

To determine whether the interactive visualisation of patient-specific virtual 3D models of the renal anatomy influences the pre-operative decision-making process of urological surgeons for complex renal cancer operations.

Methods

Five historic renal cancer patient pre-operative computed tomography (CT) datasets were retrospectively selected based on RENAL nephrectomy score and variety of anatomy. Interactive virtual 3D models were generated for each dataset using image segmentation software and were made available for online visualisation and manipulation. Consultant urologists were invited to participate in the survey which consisted of CT and volume-rendered images (VRI) for the control arm, and CT with segmentation overlay and the virtual 3D model for the intervention arm. A questionnaire regarding anatomical structures, surgical approach, and confidence was administered.

Results

Twenty-five participants were recruited (54% response rate), with 19/25 having > 5 years of renal surgery experience. The median anatomical clarity score increased from 3 for the control to 5 for the intervention arm. A change in planned surgical approach was reported in 19% of cases. Virtual 3D models increased surgeon confidence in the surgical decisions in 4/5 patient datasets. There was a statistically significant improvement in surgeon opinion of the potential utility for decision-making purposes of virtual 3D models as compared to VRI at the multidisciplinary team meeting, theatre planning, and intra-operative stages.

Conclusion

The use of pre-operative interactive virtual 3D models for surgery planning influences surgical decision-making. Further studies are needed to investigate if the use of these models changes renal cancer surgery outcomes.

Electronic supplementary material

The online version of this article (10.1007/s11548-019-01913-5) contains supplementary material, which is available to authorized users.

Changes in cholinergic and purinergic neurotransmission in the diabetic rabbit bladder

BACKGROUND

Diabetes mellitus (DM)-associated alterations in bladder function have been attributed to changes in autonomic receptors and alterations in detrusor structure and function. The changes in cholinergic and purinergic neurotransmission in the DM rabbit bladder were evaluated.

MATERIALS AND METHODS

DM was induced with alloxan in adult male New Zealand White rabbits. At 6 months, detrusor and bladder neck muscle strips were obtained and mounted in organ baths. Transmural electrical field stimulation (EFS: supramaximal voltage, 0.1 ms duration, 10 s trains) was performed in the presence of atropine (10(-6) M) or alpha, beta-methylene ATP (10(-6) M), and after adding tetrodotoxin10(-6) M. Purinergic, alpha, beta-methylene ATP-sensitive, and cholinergic, atropine-sensitive, components were calculated independently and compared with those from controls.

RESULTS

Both normal and DM detrusor and bladder neck strips contracted in a frequency-dependent fashion in response to transmural EFS. A plot of EFS vs. detrusor contractility showed a decrease (ANOVA < 0.001) in the cholinergic nerve-mediated component, whereas the purinergic nerve-mediated component was increased (ANOVA < 0.001) in the DM detrusor compared to the control. The total EFS- and KCl-induced responses were unaltered in the DM group compared to the controls. There was no difference in purinergic, alpha, beta-methylene ATP-sensitive, and cholinergic, atropine-sensitive, components in strips from the bladder neck for both normal and DM rabbits.

CONCLUSION

These results suggest that an enhancement of purinergic and a reduction of cholinergic neurotransmission occur in the detrusor muscle of the diabetic rabbit. These changes may contribute to the pathophysiology of diabetic cystopathy.

Down-regulation of nitric oxide synthase in the diabetic rabbit kidney: potential relevance to the early pathogenesis of diabetic nephropathy

OBJECTIVES

Nephropathy is a well-recognised complication of diabetes mellitus (DM). The aim of this study was to investigate the effect of DM on the density and distribution of nitric oxide (NO) synthase (NOS) in the rabbit kidney. Quantification of the NOS radioligand on slide-mounted sections was compared with the nitroblue tetrazolium reaction, where the intensity of the reaction varies with the nicotinamide adenine dinucleotide diaphorase (NADPH-d) activity of NOS.

MATERIALS AND METHODS

DM was induced with alloxan in six New Zealand White (NZW) rabbits. Plasma creatinine, urea and electrolytes were monitored at monthly intervals. The kidneys were removed following 6 months of DM. Transverse serial sections were cut and low-resolution autoradiography was performed using a radioligand for NOS ([(3)H]-NOARG). Histochemical localisation of NADPH-d activity was also performed. Densitometric analysis was performed on the autoradiographs and the results compared with those obtained from six age-matched control rabbits.

RESULTS

There was a significant (p < 0.01) rise in plasma creatinine levels in the diabetic rabbits, although the mean values remained within the reference range. There was a significant (p < 0.0001) down-regulation of NOS binding sites in both the cortex and medulla of the DM kidney when compared with the controls. A similar decrease in NADPH-d activity was seen in the diabetic renal cortex and medulla. In addition, NADPH-d activity also appeared to be reduced in the diabetic glomeruli when compared with controls.

CONCLUSIONS

NOS binding sites and NADPH-d activity are significantly decreased in the DM renal cortex and medulla. These changes are associated with a mild deterioration in renal function and may be an early event that could subsequently play a role in the progression of DM nephropathy. Manipulating the NO pathway during the early stages of DM nephropathy may be beneficial.

Endothelin-1 and Nitric Oxide in the Pathogenesis of Urinary Tract Disorders Secondary to Bladder Outlet Obstruction

Bladder outlet obstruction (BOO) is a common disorder that is associated with urinary tract symptoms. Nitric oxide (NO), synthesized by NO synthase (NOS) is a potent vasodilator that is present throughout the urinary tract and the corpus cavernosum. Endothelin-1 (ET-1) conversely is a potent vasoconstrictor peptide that is similarly distributed throughout the urinary tract. ET-1 and NO as well as possessing opposing actions regulate each other's synthesis. The disruption of the balance between ET-1 and NO is associated with various vascular pathologies. However, their potential roles in the pathogenesis of urinary tract disorders, secondary to BOO, is not well established. New Zealand White rabbits with BOO are considered to be a suitable model of the human condition. Hence, using this model, we systematically investigated the potential roles of ET-1 and NO in the pathogenesis of the various urological disorders associated with BOO. In this review we discuss the results of our studies, which support the concept that an imbalance between ET-1 and NO may be associated with the pathogenesis of urinary tract disorders secondary to BOO. We also discuss the potential clinical implications of this association. This review is based on the Bard Silver Medal Lecture given (by MAK) at the 2002 British Association of Urological Surgeons (BAUS) annual meeting.

Enhanced relaxation of diabetic rabbit cavernosal smooth muscle in response to nitric oxide: potential relevance to erectile dysfunction

New Zealand white rabbit cavernosal smooth muscle strips (n=6) were mounted in organ baths. Relaxations to nitric oxide (10(-7)-10(-4) mol/l) were measured and the same procedure was repeated on strips from rabbits 6 months after alloxan-induced diabetes (n=6). Transverse cavernosal sections were obtained from the same penises. Low and high resolution autoradiographs were prepared using [(3)H]-L-N(G)-nitroarginine (an index of nitric oxide binding sites) and analysed densitometrically. Histochemical analysis was performed on adjacent sections using NADPH diaphorase (an index of nitric oxide synthase activity). Nitric oxide relaxed control rabbit cavernosal smooth muscle strips in a concentration-dependent manner. Diabetic rabbit cavernosal smooth muscle strips were significantly (P<0.03) more sensitive to nitric oxide (mean IC(50)=3.9 x 10(-6) mol/l). Nitric oxide synthase binding sites were localised to the cavernosal endothelium and smooth muscle. Nitric oxide synthase activity was increased in 6 month diabetic cavernosal smooth muscle. These findings suggest impairments in the L-arginine-nitric oxide pathway may play a role in the pathophysiology of diabetic erectile dysfunction.

The effect of sildenafil on corpus cavernosal smooth muscle relaxation and cyclic GMP formation in the diabetic rabbit

Sildenafil, a type V phosphodiesterase inhibitor, enhances smooth muscle relaxation in normal human and rabbit corpus cavernosum. We investigated the in vitro effects of sildenafil on non-adrenergic, non-cholinergic and nitric oxide (NO)-mediated cavernosal smooth muscle relaxation in diabetic rabbits, since alterations in this pathway are recognised in diabetic erectile dysfunction. Diabetes mellitus was induced in male New Zealand White rabbits with alloxan. Cavernosal strips from age-matched control, 3- and 6-month diabetic animals were mounted in organ baths. Relaxation responses to electrical field stimulation (1-20 Hz) or sodium nitroprusside (10(-8)-10(-4) M) were assessed in the absence and presence of sildenafil (10(-8) and 10(-7) M). The effect of sildenafil on cGMP formation by the corpus cavernosum was also assessed following stimulation with sodium nitroprusside, A23187 and acetylcholine. Sodium nitroprusside-stimulated relaxations were significantly (P<0.03) impaired in the corpus cavernosum from both diabetic groups, (IC(50)=4.6 x 10(-6) M following 3 months of diabetes mellitus and 4.0 x 10(-6) M following 6 months of diabetes mellitus; compared to 7.5 x 10(-7) M for pooled age-matched controls). Sildenafil (10(-7) M) significantly enhanced sodium nitroprusside-stimulated relaxation in control (P<0.05) and diabetic groups (P<0.03). Electrical field stimulation-mediated relaxations of the corpus cavernosum were significantly impaired after 6-month diabetes mellitus and enhanced by sildenafil (10(-8) M). cGMP formation by the diabetic corpus cavernosum was impaired significantly, but restored towards normal by sildenafil. We suggest that the impairment of NO-mediated relaxation of the corpus cavernosum reflect, at least in part, a defect in guanylyl cyclase activity. These findings support the use of sildenafil as an effective, orally administered, treatment for diabetic erectile dysfunction.

The effect of nitric oxide and peroxynitrite on rabbit cavernosal smooth muscle relaxation

Nitric oxide (NO) mediates penile erection by inducing cavernosal smooth muscle relaxation. Superoxide anion (O2-) can influence the activity of NO by reacting with it to produce peroxynitrite (PN). This is a highly reactive species that is known to attack a variety of biological targets. It is far more reactive and damaging than its precursors. We therefore, investigated the effect of PN on rabbit cavernosal smooth muscle relaxation and compared it to NO. Cavernosal strips from nine adult New Zealand White rabbits were excised (n = 12 strips for each arm of the study) and mounted in organ baths. After pre-contraction with phenylephrine (PE) (100 microM) the strips were exposed to either NO or PN (1-100 microM) and subsequent smooth muscle relaxations monitored. Some tissues were incubated with oxadiazoloquinoxalin-1-one (ODQ; 10 microM), an inhibitor of guanylyl cyclase, before the addition of NO or PN. NO and PN induced concentration-dependent relaxations in all strips. However, PN (IC50: 26 +/- 3.6 microM) was significantly less potent than NO (IC50: 11 +/- 0.7 microM) [P < 0.01]. Relaxation induced by NO was immediate and short-lived, with the tension returning to its original level. In contrast, PN-initiated relaxations were of a slower onset and more prolonged, with the tissues unable to recover tension. However, after several washouts the tissues were fully responsive to PE. Both NO- and PN-mediated relaxations were inhibited by ODQ, suggesting the involvement of cGMP in this process. Although PN mediates cavernosal smooth muscle relaxation, it is much less potent than NO. As PN is thought to play a role in a variety of pathologies where erectile dysfunction is prominent, it may also contribute to the pathogenesis of erectile dysfunction.

Urological aspects of female sexual dysfunction

The aetiology of male sexual dysfunction has been extensively investigated over the past few decades. This has led to the development of effective treatment for this common problem. However, to date, female sexual dysfunction has received very little attention, particularly from a urological point of view. In this review, we discuss the anatomy and physiology of the female sexual organs as well as the aetiological factors that are associated with female sexual dysfunction. An improved awareness and understanding of this subject may, in the future, enable us to address female sexual dysfunction more appropriately and develop suitable treatment.

The effect of superoxide dismutase on nitric oxide-mediated and electrical field-stimulated diabetic rabbit cavernosal smooth muscle relaxation

OBJECTIVE

To investigate the effect of superoxide dismutase (SOD, the enzyme that accelerates the breakdown of the superoxide anion, O2- to H2O) on nitric oxide (NO)-mediated and electrical field stimulated (EFS) relaxation in diabetic rabbit cavernosal smooth muscle. Materials and methods Diabetes was induced with alloxan (65 mg/kg) in six adult New Zealand White rabbits. After 6 months, cavernosal smooth muscle strips from age-matched controls and diabetic animals were mounted in organ baths. After precontraction with phenylephrine (10 micromol/L) in the presence of atropine (1 micromol/L), guanethidine (5 micromol/L) and indomethacin (10 micromol/L), relaxation responses to EFS (1-20 Hz), carbachol (10(-8)-10(-4) mol/L) and sodium nitroprusside (SNP, 10(-9)-10(-4) mol/L) were assessed in the presence and absence of SOD (100 IU/mL).

RESULTS

SNP- and carbachol-mediated (endothelium-independent and -dependent, respectively) relaxations were impaired in the diabetic cavernosal smooth muscle strips compared with controls (concentration required for 50% inhibition, 1.4 micromol/L for diabetic and 0.75 micromol/L for control with SNP, and 44 micromol/L for diabetic and 0.4 micromol/L for control with carbachol). SOD significantly enhanced both SNP- and carbachol-mediated diabetic cavernosal smooth muscle relaxations (both P < 0.05). EFS-mediated relaxations were also significantly (P < 0.05) impaired in the diabetic cavernosal smooth muscle strips; these relaxations were also significantly (P < 0.05) enhanced by SOD.

CONCLUSION

NO- and EFS-mediated cavernosal smooth muscle relaxation is impaired in a rabbit model of diabetes but SOD significantly reversed the impaired relaxation. Therefore, in diabetes, the generation of reactive oxygen species may play an important role in the development of erectile dysfunction.

Altered cavernosal endothelin-B-receptor binding sites in the rabbit model of partial bladder outlet obstruction

Erectile dysfunction (ED) is a common problem that significantly affects the quality of life. Benign prostatic hyperplasia (BPH) is the commonest known benign proliferative disorder. Recently there has been growing evidence to suggest that patients with high BPH symptom scores have an increased incidence of ED. Endothelin-1 (ET-1) is a potent vasoconstrictor peptide that is thought to play an important role as a modulator of erectile physiology and dysfunction. We investigated whether there are any changes in the density and distribution of ET-1 and its receptor subtypes in the corpora cavernosa (CC) of a rabbit model of partial bladder outflow obstruction (BOO). ET-1, endothelin-A- and -B- (ET(A) and ET(B)) receptor binding sites were primarily localized to the smooth muscle cells (SMC) of the CC and the endothelium lining the cavernosal space. ET(B)-receptor binding sites were significantly decreased (p = 0.04) in the 6-week BOO cavernosal tissue. ET-1 may play a role in the pathophysiology of ED associated with BPH. This may be partly a result of enhanced vasoconstrictor actions and SMC proliferation secondary to a reduction in ET(B)-receptors. Further work is needed to evaluate this possibility.

Normal and pathological erectile function: the potential clinical role of endothelin-1 antagonists

Erectile dysfunction (ED) is a common problem, particularly in older men. The production of penile erection involves an interplay between autonomic nerves and locally released vasoactive mediators. Endothelin-1 (ET-1) is a peptide released from endothelium in the corpus cavernosum, which causes smooth muscle contraction. Recent studies have investigated the physiological significance of ET-1 in the control of erectile function and it may play a role in detumescence. There is also much evidence to link ET-1 to risk factors for ED. ET-1 antagonists may prove beneficial in the treatment of ED and also in prevention of long term deterioration of erectile function. These antagonists may also find a role when used in combination with agents, which are established for the treatment of ED.

Endothelin-1 and urinary bladder hyperplasia following partial bladder outlet obstruction

Urinary bladder hypertrophy and hyperplasia is a common feature of bladder outlet obstruction (BOO). The urinary bladder is known to synthesize endothelin-1 (ET-1). ET-1 is a potent vasoconstrictor peptide with mitogenic properties. Using an animal model of partial BOO we investigated the potential role of ET-1 and its receptor subtypes [endothelin-A and -B (ET(A) and ET(B))] in bladder vascular smooth muscle cells (SMC) proliferation. In the presence of 3-week-old BOO serum, ET(A) and ET(B) antagonists significantly (p = 0.008) inhibited detrusor and bladder neck SMC proliferation. Cell counts were significantly reduced from the detrusor (p = 0.03, p = 0.01 with ET(A) and ET(B) antagonists, respectively) and bladder neck (p = 0.01 for both ET(A) and ET(B) antagonists). These results suggest that ET-1 antagonists may prevent SMC hyperplasia associated with partial BOO.

Synchronous bilateral torsion of the appendix testis

Bilateral torsion of testicular appendages is extremely uncommon. We present a rare clinical case of bilateral synchronous torsion of the hydatids of Morgagni. Clinical management was dictated by the clinical findings.

Inhibition of diabetic bladder smooth muscle cell proliferation by endothelin receptor antagonists

Urinary bladder hypertrophy and hyperplasia are well recognised in diabetic cystopathy. The urinary bladder is known to synthesise endothelin-1 (ET-1), a potent vasoconstrictor peptide with mitogenic properties. Using diabetic New Zealand White (NZW) rabbits, we investigated the potential role of ET receptor subtypes (ETA and ET(B)) on the proliferation of bladder smooth muscle cells (SMC). Diabetes mellitus was induced in adult male NZW rabbits. After 6 months, control (n = 6) and diabetic (n = 6) bladders were removed and SMC from the dome and bladder neck were grown using standard explant methodology. At passage two, the cells were made quiescent and then further incubated in foetal calf serum (FCS), control age-matched rabbit serum (CRS) or diabetic rabbit serum (DRS) in the presence or absence of ET(A)-antagonist (BQ123) or ET(B)-antagonist (BQ788). SMC proliferation was then measured with 5-bromo-2'deoxy-uracil 24 h later and by cell counting (using a haemocytometer) at 48 h. Neither BQ123 nor BQ788 influenced detrusor or bladder neck SMC proliferation in FCS or CRS. However, in the presence of DRS, BQ123 and BQ788 significantly inhibited diabetic detrusor and bladder neck SMC proliferation at 30 and 100 nmol/l (P < 0.03 and P < 0.01, respectively). Cell counts were also significantly reduced from the diabetic detrusor and bladder neck (P < 0.01 and P < 0.03 with BQ123 and BQ788, respectively). These results suggest that ET may play a pathophysiological role in the bladder SMC hyperplasia associated with diabetes mellitus.

Doxazosin modifies serotonin-mediated rabbit urinary bladder contraction. Potential clinical relevance

5-Hydroxytryptamine (5-HT) induces rabbit detrusor contractions via 5-HT3 receptors. Similarly, 5-HT4 receptors are known to be present in the human bladder. Doxazosin, a non-selective alpha1 antagonist, is used for the symptomatic relief of bladder outflow obstruction. Previous work has shown that doxazosin inhibits 5-HT2-mediated platelet shape change. Hence, the aim of this study was to assess, using organ baths and autoradiography, whether doxazosin has any 5-HT-inhibiting activity in the rabbit detrusor. Detrusor strips from adult New Zealand White rabbits were placed in organ baths; phenoxybenzamine (10(-5) M) was added to block alpha-receptors. After KCl responses were assessed, the tissues were exposed to 10(-3) M 5-HT. Subsequently, the strips were incubated with doxazosin or ondansetron (10(-5) M; 5-HT3 antagonist) followed by a further exposure to 5-HT. In some experiments, after the initial 5-HT-induced contractions, the tissues were washed and then re-exposed to 5-HT. These latter experiments acted as controls. Low-resolution autoradiography was performed on detrusor sections to assess the effect of doxazosin on 5-HT binding. These sections were analyzed densitometrically. Doxazosin and ondansetron produced a significant reduction in 5-HT-mediated contractions. Inhibition by doxazosin was in a concentration-dependent manner. Autoradiography demonstrated a significant reduction in [3H]-5-HT binding by doxazosin. Doxazosin significantly inhibits 5-HT-mediated contractions in the rabbit detrusor. This effect appears to be mainly mediated via 5-HT3 receptor inhibition. Autoradiographic evidence suggests that doxazosin reduces 5-HT binding in the rabbit detrusor. The beneficial effects of doxazosin in bladder outflow obstruction may be due, at least in part, to 5-HT antagonism.

Possible role of endothelin-1 in the rabbit urinary bladder hyperplasia secondary to partial bladder outlet obstruction

OBJECTIVES

Urinary bladder hypertrophy and hyperplasia are common features of bladder outlet obstruction (BOO). The urinary bladder is known to synthesize endothelin-1 (ET-1), which is a potent vasoconstrictor peptide with mitogenic properties. Using an animal model of partial BOO, we investigated the potential role of ET-1 and its receptor subtypes (ET(A) and ET(B)) in bladder smooth muscle cell (SMC) proliferation.

MATERIALS AND METHODS

Partial BOO was produced in adult male New Zealand White rabbits. After 3 weeks, the bladder was removed and SMCs from the dome and bladder neck were grown using standard explant methodology. At passage 2, the cells were made quiescent and then further incubated in foetal calf serum (FCS), control age-matched rabbit serum (CRS) or partial BOO serum (BRS) in the presence or absence of ET(A)-antagonist (BQ123) or ET(B)-antagonist (BQ788). SMC proliferation was then measured 24 h later with 5-bromo-2'deoxy-uracil and by cell counting using a haemocytometer at 48 h. Immunostaining for alpha-actin was performed on detrusor and bladder neck cells to confirm the presence of smooth muscle cells.

RESULTS

BQ123 and BQ788 did not influence detrusor or bladder neck SMC proliferation in FCS or CRS. However, in the presence of BRS, BQ123 and BQ788 (100 nmol/L) significantly (p = 0.008) inhibited detrusor and bladder neck SMC proliferation. Cell counts were significantly reduced from the detrusor (p = 0.03, p = 0.01 with BQ123 and BQ788, respectively) and bladder neck (p = 0.01 for both BQ123 and BQ78).

CONCLUSIONS

These results suggest that ET antagonists may have a role in preventing SMC hyperplasia associated with partial BOO.

Relaxation of rabbit lower urinary tract smooth muscle by nitric oxide and carbon monoxide: modulation by hydrogen peroxide

Recent studies suggest that the body produces two gaseous messengers, nitric oxide (NO) and carbon monoxide (CO), both of which activate soluble guanylyl cyclase and thus modulate the activity of smooth muscle cells. In the present study, the effects of NO and CO on the smooth muscle of the lower urinary tract were compared. In addition, the modulation of tissue NO- and CO-induced relaxation by hydrogen peroxide was examined. NO, produced endogenously by electrical field stimulation (EFS) or applied exogenously as a solution, induced a concentration-dependent relaxation of rabbit cavernosal and urethral smooth muscle strips, but not of bladder tissues. The cavernosal tissue was found to be three times more sensitive to the actions of NO than the urethra. CO also induced relaxation of both tissue types, but with no apparent difference in sensitivity between the tissues. However, CO was much less potent than NO with respect to smooth muscle relaxation. The mechanism of action of the two mediators was cyclic guanosine monophosphate (cGMP)-dependent, as evidenced by enhanced formation of cGMP and inhibition of relaxation by the guanylyl cyclase inhibitor, oxadiazoloquinoxaline-1-one (ODQ.) The data suggests that NO is the dominant messenger in these tissues, but does not exclude a role for CO. In the presence of hydrogen peroxide, the relaxation responses induced by both NO and CO were significantly increased, regardless of tissue type. The mechanism for this effect is unclear, but evidence points to a requirement for the activation of guanylyl cyclase and enhanced formation of cGMP, since potentiation by the peroxide was blocked by a specific guanylyl cyclase inhibitor. We suggest that H(2)O(2) may play a positive role in the amplification or NO and CO-mediated responses.

Potential role of endothelin and nitric oxide in physiology and pathophysiology of the lower urinary tract

Endothelium-derived vasoactive mediators (endothelin-1 with its vasoconstrictive and mitogenic properties and nitric oxide with its vasodilatory and antiproliferative properties) play an important role in the regulation of vascular smooth muscle tone and cellular proliferation. Several recent studies have now demonstrated the presence of these vasoactive agents in the urinary tract where they are thought to play a prominent role in urinary tract physiology and disease. This article reviews the synthesis, localisation and actions of endothelin and nitric oxide in the lower urinary tract and examines the possible role of these mediators in disease.

Up-regulation of endothelin (ET(A) and ET(B)) receptors and down-regulation of nitric oxide synthase in the detrusor of a rabbit model of partial bladder outlet obstruction

Bladder outlet obstruction (BOO) is associated with altered bladder structure and function. Endothelin-1 (ET-1) has mitogenic and potent contractile properties. There are two ET receptors: ET(A) and ET(B). Nitric oxide synthase (NOS) is the enzyme responsible for the synthesis of nitric oxide (NO) which is involved in smooth muscle relaxation. We investigated whether there are any changes in the density of ET-receptors and NOS in the detrusor and bladder neck in a rabbit model of BOO. Partial BOO was induced in adult male New Zealand White rabbits. Sham operated age-matched rabbits acted as controls. After six weeks the urinary bladders were excised and detrusor and bladder neck sections incubated with radioligands for ET-1, ET(A) and ET(B) receptors and with [3H]-1-NOARG (a ligand for NOS). NADPH histochemistry was also performed. BOO bladder weights were significantly increased (P = 0.002). ET-1 binding and ETA receptor binding sites were significantly increased in the BOO detrusor smooth muscle (P = 0.04, P = 0.03 respectively) and urothelium (P = 0.002, P = 0.02 respectively). ET(B) receptor binding sites were also significantly increased in the BOO detrusor smooth muscle (P = 0.04). However, there was no change in the BOO bladder neck. NOS was significantly decreased in the detrusor smooth muscle (P = 0.003) and urothelium (P = 0.0002). In the bladder neck NOS was also significantly reduced in the urothelium (P = 0.003). NADPH staining was decreased in the detrusor and bladder neck. The up-regulation of ET receptors along with the down-regulation of NOS in the detrusor may contribute to the symptoms associated with BOO. Since ET-1 has a mitogenic role, especially via its ETA receptors, the increase in ETA receptors may also be involved in detrusor hyperplasia and hypertrophy in BOO. ET antagonists may therefore have a role in the treatment of patients with BOO.

Alterations in the formation of cyclic nucleotides and prostaglandins in the lower urinary tract of the diabetic rabbit

Dysfunction of the urinary bladder is a recognised complication of diabetes mellitus (DM) which has been attributed, in part, to a direct effect on bladder smooth muscle tissue. The objective of this study was to investigate the effect of alloxan-induced DM on endogenous modulators of smooth muscle tone such as cyclic AMP (cAMP), cyclic GMP (cGMP) and prostaglandins. Male New Zealand white rabbits were rendered diabetic (hyperosmolar, non-ketotic) with an i.v. injection of alloxan. After 6 months, the urinary bladders and urethrae were excised, cut into segments, incubated with stimulators and the formation of prostaglandins (PG), cAMP and cGMP measured using radioimmunoassays. PGE2 and PGI2 formation was impaired in response to arachidonic acid stimulation, whereas it was increased in response to acetylcholine in DM detrusor, bladder neck and urethra compared to controls. Cyclic AMP and cGMP formation in response to forskolin and sodium nitroprusside, respectively, was significantly reduced in the DM tissues of the lower urinary tract compared to the control. Alterations in the formation of prostaglandins, cAMP and cGMP by the smooth muscle of DM lower urinary tract suggests that these biochemical mediators may have a pathophysiological role in the urinary bladder dysfunction associated with DM.

Time-dependent up-regulation of endothelin-A receptors and down-regulation of endothelin-B receptors and nitric oxide synthase binding sites in the renal medulla of a rabbit model of partial bladder outlet obstruction: potential clinical relevance

OBJECTIVE

To assess the density of endothelin (ET) receptors (ET-1 is a potent vasoconstrictor peptide acting on two known receptors, ETA and ETB ) and nitric oxide synthase (NOS) binding sites in the kidney of a rabbit model of bladder outlet obstruction (BOO).

MATERIALS AND METHODS

Partial BOO was created in adult New Zealand White rabbits; after 1, 3, 4 and 6 weeks of BOO, kidney sections were incubated with radioligands for ET-1, ETA, ETB receptors and with [3H]-NOARG (a ligand for NOS). Autoradiographs were generated and analysed densitometrically. Sections were also assessed by NADPH histochemistry. Plasma creatinine, urea and electrolyte levels were regularly monitored. The control and 6-week BOO kidneys were also evaluated ultrastructurally by electron microscopy.

RESULTS

There was no significant change in plasma creatinine, urea and electrolyte levels. ETA and ETB receptor density was significantly greater in the medulla than in the cortex (P<0.001) in all animals. There was an up-regulation of ETA receptors (P=0.03) and down-regulation of ETB receptors (P=0.03) and NOS binding sites (P<0.001), as well as decreased NADPH staining in the medulla of 6-week partial BOO kidneys. Electron microscopy detected glomerular disruption of the obstructed kidneys.

CONCLUSION

The time-dependent changes in ETA and ETB receptors, NOS binding sites and NADPH staining in the renal medulla, as well as ultrastructural changes, occur despite normal renal function. These changes appear to be an early event and may play a role in the development of renal failure. Hence, the use of ETA receptor antagonists at this early stage may prevent the development of renal failure/impairment in BOO.

Upregulation of endothelin A receptor sites in the rabbit diabetic kidney: potential relevance to the early pathogenesis of diabetic nephropathy

BACKGROUND/AIM

Nephropathy is an important complication of diabetes mellitus (DM). The plasma endothelin 1 (ET-1) levels are increased in DM, and ET-1 may cause deleterious effects on renal function. We, therefore, investigated whether changes in ET receptors occur in the DM rabbit kidney.

METHODS

Nine adult New Zealand White rabbits were injected with alloxan, of which 6 became diabetic; the other 3 acted as alloxan-treated controls. Six age-matched healthy rabbits served as controls. At 6 months, following cervical dislocation, the kidneys were removed, and sections (cortex and medulla) were incubated with ET(A) and ET(B) radioligands to produce low- and high-resolution autoradiographs. Immunohistochemical localization of ET-1 immunoreactivity was also performed.

RESULTS

There was greater ET(A) and ET(B) receptor binding in the control (ET(A) p = 0.0003; ET(B) p < 0.0001) and DM (ET(A) p = 0.001; ET(B) p < 0.0001) rabbits in the medulla as compared with the cortex. DM kidneys showed a significant increase in ET(A), but not ET(B), binding in the cortex (p < 0.0001) and in the medulla (p < 0.0001). High-resolution autoradiographs revealed striking [(125)I]-ET-1 receptor binding predominantly to the glomeruli. Immunohistochemistry revealed dense ET-1 immunoreactivity associated with the renal tubules, but the glomeruli exhibited no staining. Alloxan-treated controls had similar results to age-matched controls.

CONCLUSION

There are regional differences in both ET(A) and ET(B) binding in control and DM kidneys. ET(A) receptor binding sites are increased in the DM kidney (cortex and medulla). ET-1 may act in a paracrine fashion on the glomeruli. These changes may contribute to the pathogenesis of diabetic nephropathy.

Time-dependent up-regulation of neuronal 5-hydroxytryptamine binding sites in the detrusor of a rabbit model of partial bladder outlet obstruction

Serotonin (5-hydroxytryptamine; 5-HT), a vasoactive bioamine with potent contractile activity, is thought to act indirectly in the urinary bladder by the stimulation of its presynaptic receptors. This results in the release of acetylcholine (ACh), which then acts on muscarinic receptors to produce bladder contractility. Bladder outlet obstruction (BOO) can lead to detrusor instability associated with denervation supersensitivity to ACh. Using a rabbit model of partial BOO, we investigated whether there were any associated changes in the neuronal 5-HT binding sites. Partial BOO was induced in adult male New Zealand White rabbits. Sham-operated age-matched rabbits acted as controls. After 1, 3 and 6 weeks the urinary bladders were excised. Detrusor sections were incubated with [(3)H]-5-HT. Autoradiographs were generated and analysed densitometrically. The presence of nerves was detected using immunohistochemistry with NF200. Autoradiography demonstrated a time-dependent, significant (P < 0.0001) up-regulation of [(3)H]-5-HT binding sites in the detrusor smooth muscle after the induction of BOO. Immunohistochemistry confirmed that the [(3)H]-5-HT binding sites were neuronal. In the rabbit model of partial BOO there was a significant time-dependent up-regulation of neuronal [(3)H]-5-HT binding sites in the detrusor. This change may influence 5-HT-mediated ACh release, resulting in increased bladder contractility. This, in turn, may play a role in detrusor instability associated with denervation post-junctional supersensitivity. These results provide a possible rationale for further investigation into the use of 5-HT antagonists in the treatment of detrusor instability associated with BOO.

The interaction of homocysteine and copper markedly inhibits the relaxation of rabbit corpus cavernosum: new risk factors for angiopathic erectile dysfunction?

OBJECTIVES

To explore whether homocysteine (HCy), an independent risk factor for atherosclerosis (the angiopathic effect of which occurs through the generation of superoxide anions and hydrogen peroxide, augmented by copper, the superoxide anions reacting with nitric oxide, NO, to produce peroxynitrite, a highly angiopathic free radical) and copper contribute to erectile dysfunction (ED) through similar mechanisms, by assessing their interactive effects on the relaxation of corpus cavernosum using organ-bath techniques.

MATERIALS AND METHODS

Cavernosal smooth muscle strips were obtained from adult New Zealand White rabbits and mounted in organ baths. After precontraction with phenylephrine (100 micromol/L), relaxation responses to carbachol or sodium nitroprusside (SNP) were assessed in the presence or absence of HCy and copper. The effects of HCy and copper in the presence of superoxide dismutase or catalase were also investigated.

RESULTS

HCy alone inhibited carbachol-stimulated (NO-dependent) but not SNP-stimulated relaxations (NO-independent). This effect of HCy was significantly augmented by copper, which alone had no effect. The combined effect of HCy and copper was significantly (P<0.05) reversed by superoxide dismutase or catalase.

CONCLUSIONS

HCy inhibited NO-mediated cavernosal smooth muscle relaxation, an effect that was potentiated by copper and reversed by superoxide dismutase or catalase. It is therefore proposed that the effect of HCy on cavernosal smooth muscle relaxation is mediated by an interaction between NO and superoxide anions. Moreover, HCy may constitute a new risk factor for angiopathic ED.

Up-regulation of endothelin-B (ETB) receptors and ETB receptor-mediated rabbit detrusor contraction in partial bladder outlet obstruction

OBJECTIVE

To investigate, in a rabbit model of bladder outlet obstruction (BOO), whether ETB receptors initiate any contractile activity, and to assess the density of these receptors.

MATERIALS AND METHODS

Partial BOO was produced in male New Zealand White rabbits, with age-matched sham-operated rabbits acting as controls. One and 3 weeks later, the detrusor and bladder neck strips were incubated in organ baths with either BQ788 (an ETB antagonist), BQ123 (an ETA antagonist) or vehicle. Concentration-response curves were constructed using IRL-1620 (a selective ETB agonist). Low-resolution autoradiography was performed on serial detrusor and bladder neck sections from control and partial BOO (3-week) rabbits using radioligands for ETA and ETB.

RESULTS

In strips from controls and after 1 week of partial BOO, IRL-1620 induced no contractions, but after 3 weeks of BOO, IRL-1620 induced significant concentration-dependent detrusor contractions (producing 12%, 25% and 70% of the KCl response at 10-8, 10-7 and 10-6 mol/L, respectively). The ETA antagonist had no effect on IRL-1620-mediated contractions. In contrast, the ETB antagonist completely abolished these contractions. Autoradiography showed the presence of ETA and ETB receptors in the detrusor and bladder neck of normal and obstructed animals, and a significant up-regulation of ETA and ETB receptors only in the obstructed detrusor smooth muscle.

CONCLUSIONS

In BOO, ETB receptors initiate detrusor contractile activity. This is a time-dependent process that may depend on the up-regulation of ETB receptors in the detrusor. Therefore, ETB receptors may play a role in the pathophysiology of partial BOO.

Alterations in the nitric oxide synthase binding sites and non-adrenergic, non-cholinergic mediated smooth muscle relaxation in the diabetic rabbit bladder outlet: possible relevance to the pathogenesis of diabetic cystopathy

PURPOSE

To investigate the effect of diabetes mellitus (DM) on the density and distribution of nitric oxide synthase (NOS) and the smooth muscle responses to non-adrenergic, non-cholinergic (NANC) nerve stimulation and exogenous nitric oxide (NO) in the rabbit lower urinary tract.

MATERIALS AND METHODS

Transverse sections of detrusor, bladder neck and urethra, from control and six months alloxan-induced DM New Zealand White rabbits were incubated with a radioligand for NOS ([3H]-L-N(G)-nitroarginine). Densitometric analysis was performed on the autoradiographs. NADPH diaphorase histochemistry was also used as a marker for NOS activity. Responses to NANC nerve stimulation (5 to 20 Hz) and to NO (10(-6) to 3x10(-4) M.) on smooth muscle strips from detrusor, bladder neck and urethra were measured in organ baths.

RESULTS

NOS binding sites were significantly (p<0.03) more dense in the bladder neck than in the detrusor in both DM and control groups. In DM bladder neck, NOS binding sites were significantly (p<0.04) increased compared with the controls. NADPH diaphorase activity appeared markedly increased in the detrusor, bladder neck and urethra of DM animals compared with controls. The mean IC50 for exogenous NO in control versus DM were not statistically different in the bladder neck (1.03x10(-4) M versus 9.8x10(-5) M) and urethra (8.1x10(-5) M versus 8.8x10(-5) M), but the relaxations to 5x10(-6) M of NO were significantly impaired (p<0.04) in the DM urethral smooth muscle. NANC nerve-mediated relaxations were significantly impaired (p<0.001) in the DM urethral smooth muscle.

CONCLUSIONS

Alterations of both the NOS binding sites and functional responses to NANC nerve stimulation suggest that NO may have a pathophysiological role in the urinary bladder dysfunction associated with DM.

Increased expression of endothelin B receptors in the diabetic rabbit urinary bladder: functional relevance

OBJECTIVES

To determine the effect of diabetes mellitus on the density and distribution of endothelin A (ETA ) and endothelin B (ETB ) receptor subtypes in the rabbit urinary bladder, and to assess the in vitro functional properties of endothelin-1 (ET-1) receptors in bladder smooth muscle strips from diabetic and healthy rabbits.

MATERIALS AND METHODS

Diabetes mellitus was induced in six male New Zealand White rabbits with alloxan and their urinary bladders excised 6 months after the induction of diabetes. On serial detrusor and bladder neck sections, low- and high-resolution autoradiography was performed using radioligands for ET-1, ETA and ETB receptors; these sections were then analysed densitometrically. The results were compared with those from six age-matched healthy control rabbits. Functional responses were investigated using isometric tension studies.

RESULTS

ETA and ETB receptor binding sites were localized to both the urothelium and smooth muscle of the detrusor and bladder neck. There were significantly more ETB receptor binding sites in the diabetic detrusor and bladder neck sections than in controls. ET-1 smooth muscle contractile responses were ETA receptor-mediated. The smooth muscle contractile responses to ET-1 were unaltered in the detrusor, but significantly impaired in the bladder neck of diabetic animals compared with controls.

CONCLUSION

Alteration in the expression of ETB receptors and in vitro contractile smooth muscle responses to ET-1 in the diabetic rabbit urinary bladder neck may play a role in the pathophysiology of diabetic cystopathy.

Role of prostaglandins in the urinary bladder: an update

Our knowledge of prostanoids is rapidly increasing. In this review we survey the factors governing the synthesis of prostanoids by the urinary bladder, their role in the maintenance of normal bladder function, the pattern of their secretion in bladder disease and the possible use of prostanoids in the treatment of bladder pathology.