In vitro characterization of the alpha-adrenoceptors in human prostate

Generation and Regulation of Spontaneous Contractions in the Prostate

Spontaneous myogenic contractions have been shown to be significantly upregulated in prostate tissue collected from men with Benign Prostatic Hyperplasia (BPH), an extremely common disorder of the ageing male. Although originally thought likely to be involved in 'housekeeping' functions, mixing prostatic secretions to prevent stagnation, these spontaneous myogenic contractions provide a novel opportunity to understand and treat BPH. This treatment potential differs from previous models, which focused exclusively on attenuating nerve-mediated neurogenic contractions. Previous studies in the rodent prostate have provided an insight into the mechanisms underlying the regulation of myogenic contractions. 'Prostatic Interstitial Cells' (PICs) within the prostate appear to generate pacemaker potentials, which arise from the summation of number of spontaneous transient depolarisations triggered by the spontaneous release of Ca²⁺ from internal stores and the opening of Ca²⁺-activated Cl^- channels. Pacemaker potentials then conduct into neighbouring smooth muscle cells to generate spontaneous slow waves. These slow waves trigger the firing of 'spike-like' action potentials, Ca²⁺ entry and contraction, which are not attenuated by blockers of neurotransmission. However, these spontaneous prostatic contractions can be modulated by the autonomic nervous system. Here, we discuss the mechanisms underlying rodent and human prostate myogenic contractions and the actions of existing and novel pharmacotherapies for the treatment of BPH. Understanding the generation of human prostatic smooth muscle tone will confirm the mechanism of action of existing drugs, inform the identification and effectiveness of new pharmacotherapies, as well as predict patient outcomes.

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.

Age-related changes in the innervation of the prostate gland: implications for prostate cancer initiation and progression

The adult prostate gland grows and develops under hormonal control while its physiological functions are controlled by the autonomic nervous system. The prostate gland receives sympathetic input via the hypogastric nerve and parasympathetic input via the pelvic nerve. In addition, the hypogastric and pelvic nerves also provide sensory inputs to the gland. This review provides a summary of the innervation of the adult prostate gland and describes the changes which occur with age and disease. Growth and development of the prostate gland is age dependent as is the occurrence of both benign prostate disease and prostate cancer. In parallel, the activity and influence of both the sympathetic and parasympathetic nervous system changes with age. The influence of the sympathetic nervous system on benign prostatic hyperplasia is well documented and this review considers the possibility of a link between changes in autonomic innervation and prostate cancer progression.

Contractility and pacemaker cells in the prostate gland

PURPOSE

We focused on the current opinion on mechanisms generating stromal tone in the prostate gland.

MATERIALS AND METHODS

We selected the guinea pig as the main species for investigation since its prostate has a high proportion of smooth muscle that undergoes age related changes similar in many respects to that in humans. The main techniques that we used were tension recording and electrophysiology.

RESULTS

We previously reported distinct electrical activity and cell types in the prostate, and speculated on their functional roles. We believe that a specialized group of c-kit immunoreactive prostatic interstitial cells that lie between glandular epithelium and smooth muscle stroma have a role similar to that of gastrointestinal interstitial cells of Cajal, generating the pacemaker signal that manifests as slow wave activity and triggers contraction in smooth muscle cells in guinea pig prostates.

CONCLUSIONS

Since changes in muscle tone are involved in the etiology of age dependent prostate specific conditions such as benign prostatic hyperplasia, knowledge of the electrical properties of the various prostatic cell types and their interactions with each other, with nerves and with the hormonal environment, and how these factors change with age is of considerable medical importance.

Animal models for benign prostatic hyperplasia

Although the etiology of benign prostatic hyperplasia (BPH) is unknown, various animal models have been used for several decades to identify potential therapeutic approaches. These models can be divided into those measuring smooth muscle tone and those measuring cellular proliferation. Animal models have played an important role in the development of the two drug classes currently approved for the treatment of BPH: the α-adrenoceptor antagonists and the steroid 5-α-reductase inhibitors. However, models measuring prostatic tone have not been particularly useful in the identification of new α-adrenoceptor antagonists having advantages over currently available drugs, and it is not certain that reduction of prostatic smooth muscle tone is responsible for the relief of BPH symptoms. A further limitation with BPH models is that prostatic hyperplasia similar to the human condition does not occur spontaneously or cannot be induced in any suitable animal species. The identification of a more useful BPH model is focused on cellular mechanisms of prostatic growth, looking similarities between humans and experimental animals.

The forefront for novel therapeutic agents based on the pathophysiology of lower urinary tract dysfunction: alpha-blockers in the treatment of male voiding dysfunction - how do they work and why do they differ in tolerability?

alpha(1)-Adrenoceptor antagonists are the mainstay of medical treatment of male voiding dysfunction which typically is attributed to benign prostatic hyperplasia. While original concepts have assumed that they relieve voiding dysfunction by relaxing prostatic smooth muscle, newer data indicate that their therapeutic effects at least partly occur independent of prostatic relaxation, perhaps involving direct effects on blood vessels, urothelium, afferent nerves, and/or smooth muscle of the urinary bladder. The adverse event profiles differ among alpha(1)-adrenoceptor antagonists, with tamsulosin having a particularly good cardiovascular tolerability. While this was originally attributed to its selectivity for alpha(1A)-adrenoceptors, it appears that alfuzosin which lacks subtype-selectivity, has a very similar tolerability. In contrast, doxazosin and terazosin, which are chemically and pharmacologically more closely related to alfuzosin than to tamsulosin, appear to have more side effects attributable to the cardiovascular system. More recent data indicate that tolerability differences between alpha(1)-adrenoceptor antagonists may at least partly relate to pharmacokinetic rather than to pharmacodynamic differences. Taken together, these data emphasize the idea that concepts about drug efficacy and tolerability despite being highly plausible may not necessarily be true and always require thorough experimental testing.

Tamsulosin versus terazosin for benign prostatic hyperplasia: a systematic review

The effectiveness and safety of tamsulosin and terazosin for patients with benign prostatic hyperplasia (BPH) was evaluated by literature review. PubMed, Embase, the Cochrane Library, Chinese biomedicine literature database (CBM), reference lists of reports, and reviews were searched for randomized controlled trials (RCTs), or quasi-RCTs of tamsulosin versus terazosin in BPH. Twelve studies involving 2,816 men were included. Outcomes included international prostate symptom score (IPSS), quality of life (QOL), maximum urinary flow rate (Q(max)), average urinary flow rate (Q(ave)), residual volume, prostate volume, and adverse effect (dizziness, severe hypotension, dry mouth). Relative risk was calculated for dichotomous data. Sensitivity analyses assessed the influence of baseline symptom severity. We found that tamsulosin is better than terazosin when assessed by IPSS (weighted mean difference (WMD)=-1.24 95% CI [- 1.98, -0.51], there was no significant difference between the two groups in QOL (WMD=0.04 95% CI [-0.16, 0.24]), Qmax (WMD=-0.38 95% CI [-1.18, 0.41]), Q(ave) (WMD=-0.39 95% CI [- 0.84, 0.06]), residual volume (WMD=-4.32 95% CI [-10.96, 2.33]), and prostate volume (WMD=-0.28 95% CI [- 3.37, 2.81]). Fewer patients receiving tamsulosin experienced dizziness (relative risk (RR) -0.38 95% CI [0.30, 0.48]), severe hypotension (RR=0.16 95% CI [0.04, 0.68]), and dry mouth (RR=0.14 95% CI [0.03, 0.77]), compared with patients receiving terazosin. Many of the high quality RCTs showed beneficial effects of tamsulosin in terms of improving IPSS. However, whether tamsulosin proves more efficacious than terazosin in long term therapy requires confirmation by additional large sample, high quality trials.

Noradrenergic vasoconstriction of pig prostatic small arteries

The current study investigated the distribution of adrenergic nerves and the action induced by noradrenaline (NA) in pig prostatic small arteries. Noradrenergic innervation was visualized using an antibody against dopamine-beta-hydroxylase (DBH), and the NA effect was studied in small arterial rings mounted in microvascular myographs for isometric force recordings. DBH-immunoreactive nerve fibers were located at the adventitia and the adventitia-media border of the vascular wall. Electrical field stimulation (EFS, 1-32 Hz) evoked frequency-dependent contractions that were reduced by guanethidine and prazosin (adrenergic neurotransmission and alpha1-adrenoceptors blockers, respectively) and by the alpha2-adrenoceptor agonist UK 14,304. The alpha2-adrenoceptor antagonist rauwolscine reversed the UK 14,304-produced inhibition. NA produced endothelium-independent contractions that were antagonized with low estimated affinities and Schild slopes different from unity by prazosin and the alpha1A-adrenoceptor antagonist N-[2-(2-cyclopropylmethoxyphenoxy)ethyl]-5-chloro-alpha-alpha-dimethyl-1H-indole-3-ethanamine (RS 17053). The alpha1A-adrenoceptor antagonist 5-methyl-3-[3-[4-[2-(2,2,2,-trifluoroethoxy) phenyl]-1-piperazinyl]propyl]-2,4-(1H)-pyrimidinedione (RS 100329), which also displays high affinity for alpha1L-adrenoceptors, and the alpha1L-adrenoceptor antagonist tamsulosin, which also has high affinity for alpha1A- and alpha1D-adrenoceptors, induced rightward shifts with high affinity of the contraction-response curve to NA. The alpha1D-adrenoceptor antagonist 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]8-azaspiro[4,5]decane-7,9-dione dihydrochloride (BMY 7378) failed to modify the NA contractions that were inhibited by extracellular Ca2+ removal and by voltage-activated (L-type) Ca2+ channel blockade. These data suggest that pig prostatic resistance arteries have a rich noradrenergic innervation; and NA, whose release is modulated by prejunctional alpha2-adrenoceptors, evokes contraction mainly through activation of muscle alpha1L-adrenoceptors coupled to extracellular Ca2+ entry via voltage (L-type)- and non-voltage-activated Ca2+ channels.

Identification of alpha-1L and alpha-1A adrenoceptors in human prostate by tissue segment binding

PURPOSE

Silodosin (KMD-3213 or [(-)-1-(3-hydroxypropyl)-5-[(2R)-2-({2-[2-(2,2,2trifluoroethoxy)phenoxy]ethyl}amino)propyl]-2,3-dihydro-1H-indole-7-carboxamide]) (Kissei Pharmaceutical Co., Ltd., Matsumoto, Japan) is a selective antagonist for alpha-1A and alpha-1L adrenoceptors. Using this tritiated ligand the 2 alpha-1 adrenoceptors were examined in binding studies with intact tissue segments and membrane preparations of human prostate, and compared with functionally identified alpha-1 adrenoceptor.

MATERIALS AND METHODS

Binding assays with tissue segments and membrane preparations of human prostate samples were performed using [3H]-silodosin and binding affinities for various drugs were estimated. In functional experiments antagonist affinities were evaluated from the inhibitory potency against the contractile response to noradrenaline.

RESULTS

[3H]-silodosin bound to intact segments and membrane preparations of human prostate with subnanomolar affinity. [3H]-silodosin binding sites in intact segments were divided into 2 distinct components with different affinities for prazosin and RS-17053 (N-[2(2-cyclopropylmethoxyphenoxy)ethyl]-5-chloro-alpha, alpha-dimethyl1H-indole-3-ethanamine hydrochloride) (Research Biochemicals International, Natick, Massachusetts), while binding in membrane preparations showed single high affinity for these drugs. [3H]-silodosin binding sites also showed high affinity for silodosin and tamsulosin but low sensitivity to BMY 7378 (8-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-8-azaspiro(4.5)decane-7,9-dione) (Research Biochemicals International) in intact segments and in membrane preparations. In functional experiments silodosin and tamsulosin potently inhibited the contractile response to noradrenaline but prazosin, RS-17053 and BMY 7378 showed low antagonistic affinity.

CONCLUSIONS

The current binding studies in human prostate samples clearly show that alpha-1L and alpha-1A adrenoceptors coexist as pharmacologically distinct entities in intact tissues but not in crude membrane preparations. Also, alpha-1 adrenoceptors involved in the contractile response to noradrenaline are the alpha-1L subtype.

Alpha1-, alpha2- and beta-adrenoceptors in the urinary bladder, urethra and prostate

1 We have systematically reviewed the presence, functional responses and regulation of alpha(1)-, alpha(2)- and beta-adrenoceptors in the bladder, urethra and prostate, with special emphasis on human tissues and receptor subtypes. 2 Alpha(1)-adrenoceptors are only poorly expressed and play a limited functional role in the detrusor. Alpha(1)-adrenoceptors, particularly their alpha(1A)-subtype, show a more pronounced expression and promote contraction of the bladder neck, urethra and prostate to enhance bladder outlet resistance, particularly in elderly men with enlarged prostates. Alpha(1)-adrenoceptor agonists are important in the treatment of symptoms of benign prostatic hyperplasia, but their beneficial effects may involve receptors within and outside the prostate. 3 Alpha(2)-adrenoceptors, mainly their alpha(2A)-subtype, are expressed in bladder, urethra and prostate. They mediate pre-junctional inhibition of neurotransmitter release and also a weak contractile effect in the urethra of some species, but not humans. Their overall post-junctional function in the lower urinary tract remains largely unclear. 4 Beta-adrenoceptors mediate relaxation of smooth muscle in the bladder, urethra and prostate. The available tools have limited the unequivocal identification of receptor subtypes at the protein and functional levels, but it appears that the beta(3)- and beta(2)-subtypes are important in the human bladder and urethra, respectively. Beta(3)-adrenoceptor agonists are promising drug candidates for the treatment of the overactive bladder. 5 We propose that the overall function of adrenoceptors in the lower urinary tract is to promote urinary continence. Further elucidation of the functional roles of their subtypes will help a better understanding of voiding dysfunction and its treatment.

Benign prostatic hyperplasia: an insight into current investigational medical therapies

Benign prostatic hyperplasia (BPH) is a leading disorder of the elderly male population that is characterised by a progressive enlargement of prostatic tissue, resulting in obstruction of the proximal urethra and causing urinary flow disturbances. The pathophysiology of BPH associated with lower urinary tract symptoms is characterised by increased adrenergic tone (dynamic component) leading to smooth muscle contraction and prostatic overgrowth due to androgenic stimulation (static component); therefore, the therapeutic armamentarium of BPH can be broadly divided into antiadrenergic and antiandrogenic approaches. alpha1-Adrenoceptor antagonists and 5alpha-reductase inhibitors are well-established representatives of the two categories, respectively. Other antiandrogenic approaches involve gonadotropin-releasing hormone agonists and antagonists for the treatment of prostate hyperplasia. Apart from these approaches, new approaches with novel targets are emerging. The advent of new therapies is, however, more oriented towards the static component. These involve metabolic factors (hexokinase inhibitor), growth factors (vitamin D3 analogues), oxytocin antagonists and gonadotropin-releasing hormone Gi agonist-based therapies. Gene therapy and photodynamic therapies are other emerging therapies for relieving symptoms in BPH patients. With the initial success of upcoming targets, the unmet need to develop an efficacious and relatively safe therapeutic modality is discussed. Nevertheless, their long-term safety and efficacy needs to be evaluated in large-scale clinical trials. The future also belongs to combination therapies to combat both dynamic and static disease components and for extended indications such as micturition disorder and non-bacterial prostatitis.

Effect of tamsulosin on the number and intensity of ureteral colic in patients with lower ureteral calculus

BACKGROUND

We aimed to objectively determine whether tamsulosin as an alpha(1)-blocker was effective in patients who had ureterolithiasis located in the lower part of the ureter.

METHODS

Sixty patients with lower ureteral calculi (juxtavesical or intramural portion) were included in the present study. Conservative treatment, such as hydration and tenoxicam as a non-steroidal anti-inflammatory drug, was given to group 1 (30 patients). Group 2 (30 patients) was given tamsulosin (0.4 mg daily) in addition to the conservative treatment. All patients were followed up and questioned about the numbers and intensity of ureteral colic, and the rates of spontaneous passage after the procedure.

RESULTS

Spontaneous passage was observed in 22 of the 30 patients in group 1 (73.3%) and 26 of the 30 patients in group 2 (86.6%). The difference within groups 1 and 2 was not significant (P=0.196). The difference between both groups was not statistically significant either, with the stone diameter being 6 mm (P=0.635) or >6 mm (P=0.407). As group 1 patients were passing their stones, they had more ureteral colic episodes than group 2 patients. This difference was statistically significant and correlated well with the administration of tamsulosin (P=0.038). Group 1 patients reported higher scores according to a visual analog scale than group 2 patients. Also, this difference was statistically significant (P=0.000).

CONCLUSIONS

We think that the treatment of alpha(1)-blockers decreased the number of ureteral colic episodes and the intensity of pain during spontaneous passage at the lower ureteral calculi. Also, it will be beneficial to patients' quality of life.

Stress, hostility, and disease parameters of benign prostatic hyperplasia

OBJECTIVE

Psychological factors such as stress are known to influence activity in the sympathetic nervous system and hypothalamic-pituitary-gonadal axis, systems that in turn have been implicated in the development of benign prostatic hyperplasia (BPH). Associations between psychological stress and prostate function have not been directly examined. The objective of this study was to examine associations among stress, hostility, and BPH disease parameters.

METHODS

Eighty-three men diagnosed with BPH completed self-report and interview measures of stress and hostility followed by measures of urologic function.

RESULTS

Higher lifetime stress was associated with lower prostate volumes and residual urine volumes (p's < .05). By contrast, high recent stress and hostility were associated with greater residual urine (p's < .05). Stress and hostility were not associated with self-report ratings of urologic symptoms.

CONCLUSIONS

Stress and hostility were associated with objective measures of urologic functioning among men with BPH. Results highlight the need for increased attention in research and clinical settings toward associations between psychological factors and urologic disease.

Phenoxybenzamine and benextramine, but not 4-diphenylacetoxy-N-[2-chloroethyl]piperidine hydrochloride, display irreversible noncompetitive antagonism at G protein-coupled receptors

Many irreversible antagonists have been shown to inactivate G protein-coupled receptors (GPCRs) and used to study agonists and spare receptors. Presumably, they bind to primary (agonist) binding sites on the GPCR, although noncompetitive mechanisms of antagonism have been demonstrated but not thoroughly investigated. We studied noncompetitive antagonism by phenoxybenzamine and benextramine at alpha(2A)-adrenoceptors in stably transfected Chinese hamster ovary cells, benextramine and 4-diphenylacetoxy-N-[2-chloroethyl]piperidine hydrochloride (4-DAMP mustard) at endogenous muscarinic acetylcholine (mACh) receptors in human neuroblastoma SH-SY5Y cells, and benextramine at serotonin 5-HT(2A) receptors in stably transfected SH-SY5Y cells. Primary binding sites were protected by reversible competitive antagonists during pretreatment with irreversible antagonists. We conducted appropriate radioligand binding assays by measuring remaining primary binding sites and agonist affinity, functional assays to evaluate agonist-induced responses, and constitutive guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS)-Galpha(o) binding assays to determine remaining G protein activity. Phenoxybenzamine (100 microM; 20 min) and benextramine (10 or 100 microM; 20 min) at alpha(2A)-adrenoceptors, but not 4-DAMP mustard (100 nM; 120 min) at mACh receptors, displayed irreversible noncompetitive antagonism in addition to their known irreversible competitive antagonism. Although agonist binding affinity is not influenced, signal transduction is modulated in a G protein-dependent manner via allotopic interactions. Benextramine noncompetitively inhibits agonist-induced responses at three different GPCR types (alpha(2A), mACh, and 5-HT(2A) receptors) that signal via three families of G proteins (G(i/o), G(s), and G(q/11)). We conclude that, where irreversible antagonists are utilized to study drug-receptor interaction mechanisms, the presence of significant irreversible noncompetitive antagonism may influence the interpretation of results under the experimental conditions used.

Treatment of benign prostatic hyperplasia in hypertensive men

As the proportion of the US population over the age of 65 continues to rise, it is likely that the number of individuals with concomitant benign prostatic hyperplasia and hypertension will also increase. To reduce morbidity and mortality, it is important to treat patients with hypertension optimally. Evidence from outcome trials suggests that alpha1 blockers should not be used as first-line antihypertensive therapy. Although some clinicians previously recommended alpha1 blocker monotherapy for patients with both hypertension and benign prostatic hyperplasia, the most recent American Urologic Association and Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure guidelines recommend independent treatment with the most appropriate pharmacologic agents for each condition. When treating patients with benign prostatic hyperplasia, clinicians should be aware of the potential impacts that alpha1 blockers may have on blood pressure and potential adverse events in patients who are normotensive as well as in patients with treated hypertension.

Recent advances in the identification of a 1- and a 2-adrenoceptor subtypes: therapeutic implications

The cloning of multiple subtypes of both alpha1- and alpha2-adrenoceptors has renewed interest in the therapeutic application of agents interacting with these receptors. Effort has primarily been directed towards the design of uroselective alpha1-adrenoceptor antagonists for the treatment of benign prostatic hyperplasia (BPH). Evidence is accumulating for the involvement of a novel alpha1-adrenoceptor, designated as alpha1L-adrenoceptor, in alpha1-adrenoceptor-mediated smooth muscle contraction in prostatic and other urogenital tissues. While several antagonists showing a high degree of uroselectivity in animal models have been identified, their clinical superiority over the currently available alpha1-adrenoceptor antagonists has not yet been demonstrated. It is possible that the interaction with alpha1-adrenoceptors, as yet uncharacterised subtypes, at non-prostatic sites contributes to the therapeutic activity of this drug class in BPH. The alpha1-adrenoceptor subtypes involved in the control of vascular tone are currently being evaluated, and the profile of interaction with the various alpha1-adrenoceptor subtypes may play a key role in the efficacy of cardiovascular drugs such as carvedilol. Alpha2-adrenoceptor agonists are now being employed for a variety of therapeutic applications, most involving actions on receptors within the central nervous system (CNS). These agents are useful in the treatment of hypertension, glaucoma, opiate withdrawal and attention deficit hyperactivity disorder (ADHD), and as analgesics and adjuncts to general anaesthesia. While subtype selectivity has not yet been applied to the design of new alpha2-adrenoceptor agonists for these applications, recent gene mutation/knock-out experiments have identified the alpha2-subtypes involved in some of these actions, and optimisation of a therapeutic profile may be possible. Furthermore, the design of agents combining affinities for multiple adrenoceptor subtypes, or the combination of a specific adrenoceptor affinity profile with another pharmacological action, may offer advantages over molecules selective for an individual adrenoceptor subtype.

A1 and A2A adenosine receptor modulation of alpha 1-adrenoceptor-mediated contractility in human cultured prostatic stromal cells

1. This study investigated the possibility that adenosine receptors modulate the alpha(1)-adrenoceptor-mediated contractility of human cultured prostatic stromal cells (HCPSC). 2. The nonselective adenosine receptor agonist, 5'-N-ethylcarboxamido-adenosine (NECA; 10 nm-10 microm), and the A(1) adenosine receptor selective agonist, cyclopentyladenosine (CPA; 10 nm-10 microm), elicited significant contractions in HCPSC, with maximum contractile responses of 18+/-3% and 17+/-2% reduction in initial cell length, respectively. 3. In the presence of a threshold concentration of phenylephrine (PE) (100 nm), CPA (1 nm-10 microm) caused contractions, with an EC(50) of 124+/-12 nm and maximum contractile response of 37+/-4%. The A(1) adenosine receptor-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX 100 nm) blocked this effect. In the presence of DPCPX (100 nm), NECA (1 nm-10 microm) inhibited contractions elicited by a submaximal concentration of PE (10 microm), with an IC(50) of 48+/-2 nm. The A(2A) adenosine receptor-selective antagonist 4-(2-[7-amino-2-[furyl][1,2,4]triazolo[2,3-alpha][1,3,5,]triazin-5-yl amino]ethyl)phenol (Zm241385 100 nm) blocked this effect. 4. In BCECF-AM (10 microm)-loaded cells, both CPA (100 pM-1 microm) and NECA (100 pm-10 microm) elicited concentration-dependent decreases in intracellular pH (pH(i)), with EC(50) values of 3.1+/-0.3 and 6.0+/-0.3 nm, respectively. The response to NECA was blocked by Zm241385 (100 nm; apparent pK(B) of 9.4+/-0.4), but not by DPCPX (100 nm). The maximum response to CPA was blocked by DPCPX (100 nm), and unaffected by Zm241385 (100 nm). 5. NECA (10 nm-10 microm) alone did not increase [(3)H]-cAMP in HCPSC. In the presence of DPCPX (100 nm), NECA (10 nm-10 microm) caused a concentration dependent increase in [(3)H]-cAMP, with an EC(50) of 1.2+/-0.1 microm. This response was inhibited by Zm241385 (100 nm). CPA (10 nm-10 microm) had no effect on cAMP, in the presence or absence of forskolin (1 microm). 6. These findings are consistent with a role for adenosine receptors in the modulation of adrenoceptor-mediated contractility in human prostate-derived cells.

Changing aspects in the evaluation and treatment of patients with benign prostatic hyperplasia

Lower urinary tract symptoms are a common clinical symptom among men and a frequent reason for referring to a urologist. The most important information comes from the patient history because evaluation of symptoms is fundamental in the diagnosis and treatment planning for LUTS. Other aspects of the initial evaluation, such as the physical examination and initial laboratory values, can provide valuable additional information about the severity of the disease and the need for treatment. If treatment is warranted based on this information, additional diagnostic tests may be appropriate to set a pretreatment baseline, rule out other conditions, and plan treatment approach. Fortunately, a variety of effective medical and surgical treatments are available to treat this common disease.

Alpha 1-adrenoceptor effects mediated by protein kinase C alpha in human cultured prostatic stromal cells

1 We have investigated the effects of alpha(1)-adrenoceptor stimulation upon contractility, Ca(2+) influx, inositol phosphate production, and protein kinase C (PKC) translocation in human cultured prostatic stromal cells (HCPSC). 2 The alpha(1)-adrenoceptor selective agonist phenylephrine elicited contractile responses of HCPSC, i.e. a maximal cell shortening of 45+/-6% of initial cell length, with an EC(50) of 1.6+/-0.1 microM. The alpha(1)-adrenoceptor selective antagonists prazosin (1 microM) and terazosin (1 microM) both blocked contractions to phenylephrine (10 microM). The L-type calcium channel blocker nifedipine (10 microM), and the PKC inhibitors Gö 6976 (1 microM) and bisindolylmaleimide (1 microM) also inhibited phenylephrine-induced contractions. 3 Phenylephrine caused a concentration dependent increase in inositol phosphate production (EC(50) 119+/-67 nM). This response was blocked by terazosin (1 microM). 4 Phenylephrine caused the translocation of the PKC alpha isoform, but not the beta, delta, gamma, epsilon or lambda isoforms, from the cytosolic to the particulate fraction of HCPSC, with an EC(50) of 5.7+/-0.5 microM. 5 In FURA-2AM (5 microM) loaded cells, phenylephrine elicited concentration dependent increases in [Ca(2+)](i), with an EC(50) of 3.9+/-0.4 microM. The response to phenylephrine (10 microM) was blocked by prazosin (1 microM), bisindolymaleimide (1 microM), and nifedipine (10 microM). 6 In conclusion, this study has shown that HCPSC express functional alpha(1)-adrenoceptors, and that the intracellular pathways responsible for contractility may be largely dependent upon protein kinase C activation and subsequent opening of L-type calcium channels.

Enhancement of alpha-adrenoceptor-mediated responses in prostate of testosterone-treated rat

The present study was undertaken to investigate the effect of testosterone on the alpha-adrenoceptor-mediated contractile responses in ventral lobe of rat prostate. Contractile responses to various alpha-adrenoceptor agonists (phenylephrine, A61603 (N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl] methanesulphonamide), clonidine, guanfacine, ST587 ((2,3-dihydro-benzo[1,4]dioxin-2-ylmethyl)-[2-(2,6-dimethoxy-phenoxy)-ethyl]-amine) and xylazine) were tested in prostate strips obtained from control and testosterone (3 mg/kg, s.c. 5 days a week for 15 days-10 doses total)-treated rats. Dose-response curves for alpha-adrenoceptor agonists in testosterone-treated animals showed a leftward shift, indicating increased sensitivity of tissue to alpha-adrenoceptor agonists. To find the mechanism of increased sensitivity, K(A) value and receptor reserve of phenylephrine were estimated. Neither the K(A) value nor the receptor reserve of phenylephrine was altered in testosterone-treated rats. The concentration-occupancy curve for A61603 was shifted leftward and the K(A) value for A61603 decreased about four-fold. The K(B) value of 2-(2,6-dimethoxyphenoxyethyl) aminomethyl-1,4-benzodioxane (WB4101) was not altered, however, the K(B) value for prazosin was decreased approximately 5.5-fold. These findings indicate that the testosterone-mediated increase in sensitivity of prostate to alpha-adrenoceptor agonists is due to alterations in the alpha(1)-adrenoceptor pool.

Characterization of some novel alpha 1-adrenoceptor antagonists in human hyperplastic prostate

We synthesized some quinazoline-based compounds, such as FH-71 (ethyl 4-(3-(4-(2-methoxyphenyl)piperazinyl)aminoquinazolin-2-carboxylate), EW-65 (4-(3-(4-(2-methoxyphenyl)piperazinyl)propyl)aminoquinazolin-2-carboxamide) and EW-154 (2-(4-(4-(2-methoxyphenyl)piperazinyl)butyl)amino-4-cyclohexylamino-quinazolin), and then characterized their pharmacological properties in several tissues. All of these compounds produced potent inhibition of phenylephrine but not high K(+) or U46619 (11 alpha,9 alpha-epoxymethano-15S-hydroxy-prosta-5Z,13E-dienoic acid)-induced contractions in rat aorta, suggesting alpha(1)-adrenoceptor antagonist properties. With rat vasa deferentia and spleens as the functional alpha(1A)- and alpha(1B)-adrenoceptor models, respectively, FH-71 exhibited greater antagonistic potency in rat vas deferens, EW-154 in rat spleen, and EW-65 had similar effects in both tissues. The potency ratios of terazosin, FH-71, EW-65 and EW-154 against phenylephrine-induced contractions in rat vas deferens/spleen were 1, 19.04, 0.39 and 0.09, respectively. The results suggest that FH-71 is a selective alpha(1A)-adrenoceptor antagonist, whereas EW-154 exhibits more antagonistic selectivity against alpha(1B)-adrenoceptors. FH-71 also showed a greater potency than EW-65 and EW-154 against phenylephrine-induced contraction in human hyperplastic prostate. The pA(2) values were 8.34, 7.44 and 7.05, respectively. Furthermore, FH-71 and EW-65 were not cytotoxic whereas EW-154 (all in 10 microM) had a massive toxic effect (more than 80%) in human prostatic smooth muscle cells. These data show FH-71 to be a potent and selective alpha(1A)-adrenoceptor antagonist with activity in human hyperplastic prostate.

Efficacy and tolerability of drugs for treatment of benign prostatic hyperplasia

It has long been recognised that neural factors are of considerable importance in lower urinary tract function. Whilst reduction in the bulk of the human prostate is feasible, experience on this therapeutic approach proved to be disappointing. Existing trial data with the agent finasteride are reviewed. A number of formulations derived from plant extracts have been advocated but their mechanism of action remain largely obscure and there is a dearth of placebo controlled information to support their efficacy. Experience over the last 10 years has demonstrated efficacy with the use of alpha adrenoceptor blockade in the management of BPH. Alpha adrenoceptor antagonists relax the prostatic smooth muscle by interrupting the sympathetic pathway at the receptor level. Recent developments in this field include the recognition that there are alpha I adrenoceptor subtypes. The functional adrenoceptor in the human prostate is predominantly the alpha IA - subtype. Of the alpha 1-adrenoceptor antagonists only tamsulosin discriminates between the alpha 1-adrenoceptor subtypes. Alpha 1-blockers should be used in first-line medical therapy for BPH and 5-alpha-reductase inhibitors reserved for those patients in whom alpha-blocker therapy fails. Alpha I-blockers such as doxazosin, tamsulosin, terazosin, alfuzosin are effective in the treatment of BPH both in younger and in older men. The drugs are well tolerated. The majority of side effects were classified as minor and mild. The most common complaints, as with other alpha-blockers, are dizziness, fatigue and headache, and these are often transient. In contrast, finasteride can lead to impotence, reduced libido. gynaecomastia or ejaculatory disorders. Men with small prostates may not be suitable candidates for finasteride therapy.

Hormonal effects of Z-350, possessing steroid 5alpha-reductase inhibitory and alpha1-adrenoceptor antagonistic actions, in the rat

We examined the hormonal effects of Z-350, (S)-4-[3-(4-[1-(4-methylphenyl)-3-[4-(2-methoxyphenyl)piperazine-1-yl]propoxy]benzoyl)indole-1-yl]butyric acid hydrochloride, which has both alpha1-adrenoceptor blocking activity and steroid 5alpha-reductase inhibitory activity, in male and female rats. Z-350 administered orally for 14 days at a dose of 30 mg/kg to normal male rats significantly reduced the weight of the prostate and seminal vesicles without affecting the weight of the testis, epididymis, adrenals, kidney or liver. Prostatic levels of dihydrotestosterone decreased dose-dependently, with a slight increase in the level of testosterone at a Z-350 dose of 100 mg/kg. We observed no effects on the weight of the prostate in castrated rats or on the weight of the uterus in normal or 17beta-estradiol-treated female rats. These results suggest that Z-350 inhibits prostatic growth via inhibition of steroid 5-reductase without other hormonal effects.

The autonomic and sensory innervation of the smooth muscle of the prostate gland: a review of pharmacological and histological studies

1. We review literature demonstrating (a) the presence and (b) the actions of substances that mediate or modify neuroeffector transmission to the smooth muscle of the prostrate stroma of a number of species including man. 2. In all species studied prostatic stroma, but not secretory acini, receives rich noradrenergic innervation. Stimulation of these nerves causes contractions of prostate smooth muscle that are inhibited by guanethidine and by alpha1-adrenoceptor antagonists that probably act at the alpha1L-adrenoceptor. Such actions underlie the clinical use of alpha1-adrenoceptor antagonists in benign prostatic hyperplasia (BPH). 3. Acetylcholinesterase-positive nerves innervate prostatic stroma as well as epithelium. Atropine reduces nerve-mediated contractions of stromal muscle in the rat, guinea-pig and rabbit. M1, M2 and M3 muscarinic receptors have been implicated in eliciting or facilitating contraction in the prostate from guinea-pig, dog and rat, respectively. 4. Adenine nucleotides and nucleosides, nitric oxide (NO), opioids, neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) may act as co-transmitters or modulators in autonomic effector nerves supplying prostate stroma. Adenosine inhibits neurotransmission to the rat prostate, and NO is inhibitory in prostate from human, rat, rabbit, pig and dog. The activity of peptides present in the relatively sparse sensory innervation of the prostate exhibits species variation, but, when effective, calcitonin gene-related peptide is inhibitory while tachykinins are stimulant. The roles of NPY and VIP in modulating stromal contractility remain unclear. 5. Taken together the current literature indicates that, in addition to noradrenaline, other neurotransmitters and neuromodulators may regulate the tone of prostatic smooth muscle. Whether drugs that mimic or modify their actions might be useful in providing symptomatic relief of the urinary symptoms associated with BPH remains to be established.

Effect of JTH-601, a novel alpha(1)-adrenoceptor antagonist, on prostate function in dogs

We examined the effect of JTH-601 (3-¿N-[2-(4-hydroxy-2-isopropyl-5-methylphenoxy)ethyl]-N-methylaminom ethyl¿-4-methoxy-2,5,6-trimethylphenol hemifumarate), a new alpha(1L)-adrenoceptor antagonist, on prostatic function in isolated canine prostate and in anesthetized dogs. In the contraction study, phenylephrine and noradrenaline produced concentration-dependent contractions in canine prostate and carotid artery, respectively. In these tissues, JTH-601, prazosin (a non-selective alpha(1)-adrenoceptor antagonist), and tamsulosin (an alpha(1A)-adrenoceptor antagonist) competitively antagonized contraction in a concentration-dependent manner. The pA(2) (pK(B)) values with prostate were 8.49+/-0.07 for JTH-601, 7.94+/-0.04 for prazosin and 9.42+/-0.22 for tamsulosin. The ratio of pA(2) (carotid artery/prostate), i.e. prostatic selectivity, was 10.471 for JTH-601, 0.008 for prazosin and 0.371 for tamsulosin, respectively. In anesthetized dogs, JTH-601 (1 mg/kg, i.d.) significantly decreased urethral pressure by 15% without affecting blood pressure or heart rate. Tamsulosin (0.1 mg/kg, i.d.) decreased urethral pressure to the same extent as did JTH-601, but with a significant effect on blood pressure and heart rate. JTH-601 showed higher selectivity for canine prostate both in vitro and in vivo. In prostate, an important role of the alpha(1L)-adrenoceptor is suggested in the smooth muscle contraction mediated by alpha(1)-adrenoceptors. JTH-601 is expected to be an effective alpha(1)-adrenoceptor antagonist for the treatment of urinary outlet obstruction by benign prostatic hypertrophy with a minimum effect on the cardiovascular system.

Adrenoceptor subclassification: an approach to improved cardiovascular therapeutics

The subdivision of alpha adrenoceptors into the alpha 1 and alpha 2 classes was the impetus for the design of the selective alpha 1-adrenoceptor antagonists, which remain useful antihypertensives. alpha 2-Adrenoceptor agonists also have application as antihypertensive drugs, based on their ability to reduce sympathetic outflow. Likewise, subdivision of the beta adrenoceptors has lead to the development of selective beta 1-adrenoceptor antagonists as antihypertensive and selective beta 2 agonists as bronchodilators. In the past decade, both the alpha 1 and alpha 2 adrenoceptors have been further subdivided, each into three subclasses. In addition, there is strong functional evidence to suggest the presence of additional adrenoceptor subtypes, such as the "alpha 1L" adrenoceptor and "beta 4" adrenoceptor. alpha 1A (or alpha 1L)-Adrenoceptor antagonists have been evaluated for benign prostatic hyperplasia (BPH), and selective alpha 1A agonists for stress incontinence. Gene knockout experiments in mice suggest an important role for the alpha 1B adrenoceptor in the control of vascular tone. Hence, selective alpha 1B antagonists may offer a new approach toward hypertension. Although targeting of specific adrenoceptors can be used to optimize the therapeutic profile of a drug, there are also cases where blockade of multiple adrenoceptors is desirable, as with the alpha/beta-adrenoceptor antagonist carvedilol in congestive heart failure. It is possible that combination of affinities for selected adrenoceptor subtypes within a single molecule may be desirable for certain applications.

Investigation of the effects of some alkaloidal alpha1-adrenoceptor antagonists on human hyperplastic prostate

The effects of N-allylsecoboldine, (-)-discretamine, ( )-govadine and [(+/-)-2,3,10,11-tetrahydroxytetrahydroproto-berberine HBr] ((+/-)-THP) on contractile responses were investigated in human hyperplastic prostate. They all inhibited, concentration dependently, the tension responses to phenylephrine and electrical field stimulation, and the pA2 and pIC50 values were calculated. The relative potencies of these four agents with reference to prazosin were obtained. The results showed that N-allylsecoboldine exhibited greater potency (4.1-fold), whereas (-)-discretamine, (+/-)-govadine and (+/-)-THP had similar potencies, against contractions elicited by electrical field stimulation and against contractions elicited by phenylephrine in human hyperplastic prostate. In addition, the potency ratios of N-allylsecoboldine, (-)-discretamine, (+/-)-govadine and (+/-)-THP against phenylephrine-induced contractions in rat vas deferens/spleen were 7.78, 0.89, 0.57, and 0.96, respectively. In the presence of prazosin (0.3 +/-M) to block alpha1-adrenoceptor-mediated responses, nifedipine (10 microM), but not the above four agents, significantly blocked KCl (60 mM)-induced tension responses in human hyperplastic prostate. It is suggested that N-allylsecoboldine exhibits greater potency against nerve-mediated contraction than against phenylephrine-induced contraction in human hyperplastic prostate and that this antagonistic effect is due mainly to its high affinity for the alpha1A-adrenoceptor subtype.

Naftopidil, a novel alpha1-adrenoceptor antagonist, displays selective inhibition of canine prostatic pressure and high affinity binding to cloned human alpha1-adrenoceptors

The pharmacological profiles of the alpha1-adrenoceptor antagonists naftopidil, tamsulosin and prazosin were studied in an anesthetized dog model that allowed the simultaneous assessment of their antagonist potency against phenylephrine-mediated increases in prostatic pressure and mean blood pressure. The intravenous administration of each of these compounds dose-dependently inhibited phenylephrine-induced increases in prostatic pressure and mean blood pressure. To further assess the ability of the three compounds to inhibit phenylephrine-induced responses, the doses required to produce a 50% inhibition of the phenylephrine-induced increases in prostatic and mean blood pressure and the selectivity index obtained from the ratio of those two doses were determined for each test compound. Forty minutes after the intravenous administration of naftopidil, the selectivity index was 3.76, and those of tamsulosin and prazosin were 1.23 and 0.61, respectively. These findings demonstrated that naftopidil selectively inhibited the phenylephrine-induced increase in prostatic pressure compared with mean blood pressure in the anesthetized dog model. The selectivity of naftopidil for prostatic pressure was the most potent among the test compounds. In addition, using cloned human alpha1-adrenoceptor subtypes, naftopidil was selective for the alpha1d-adrenoceptor with approximately 3- and 17-fold higher affinity than for the alpha1a- and alpha1b-adrenoceptor subtypes, respectively. The selectivity of naftopidil for prostatic pressure may be attributable to its high binding affinity for alpha1a- and alpha1d-adrenoceptor subtypes.

Binding and functional characterization of alpha1-adrenoceptor subtypes in the rat prostate

The alpha1-adrenoceptor subtypes of rat prostate were characterized in binding and functional experiments. In binding experiments, [3H]tamsulosin bound to a single class of binding sites with an affinity (pKD) of 10.79+/-0.04 and Bmax of 87+/-2 fmol mg(-1) protein. This binding was inhibited by prazosin, 2-(2,6-dimethoxy-phenoxyethyl)-aminomethyl-1,4-benzodioxane hydrochloride (WB4101), 5-methylurapidil, alpha-ethyl-3,4,5,-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy)ethyl)-amin o)-propyl)benzeneacetonitrile fumarate (HV723) and oxymetazoline with high efficacy, resulting in a good correlation with the binding characteristics of cloned alpha1a but not alpha1b and alpha1d-adrenoceptor subtypes. In functional studies, noradrenaline and oxymetazoline produced concentration-dependent contractions. These contractions were antagonized by tamsulosin, prazosin, WB4101 and 5-methylurapidil with an efficacy lower than that exhibited by these agents for inhibition of [3H]tamsulosin binding. The relationship between receptor occupancy and contractile amplitude revealed the presence of receptor reserve for noradrenaline, but the contraction induced by oxymetazoline was not in parallel with receptor occupation and developed after predicted receptor saturation. From these results, it is suggested that alpha1A-adrenoceptors are the dominant subtype in the rat prostate which can be detected with [3H]tamsulosin, but that the functional subtype mediating adrenergic contractions has the characteristics of the alpha1L-adrenoceptor subtype, having a lower affinity for prazosin and some other drugs than the alpha1A-adrenoceptor subtype.

Prevention of Postherniorrhaphy Urinary Retention with Prazosin

Urinary retention that necessitates catheterization after herniorrhaphy is a well known, but usually ignored, situation. Increased sympathetic activity resulting from surgery may be the contributing factor. Blockade of a receptors in the bladder neck and urethral sphinchter may prevent postoperative urinary retention. In this prospective placebo-controlled study, the efficacy of prazosin in preventing postoperative urinary retention after herniorrhaphy was investigated in 156 patients. Patients were randomized into two groups. Patients in Group I (control) were given placebo orally 12 hours before surgery, just before surgery, and 12 and 24 hours after surgery. In Group II, 1 mg of prazosin was given in the same manner of placebo. Nine of 84 patients (10.8%) in the prazosin group and 18 of 72 patients (25%) in the placebo group developed urinary retention. Catheterization was required in only 3 patients (3.5%) in the prazosin group compared to 10 patients (13.8%) in placebo-treated group (P < 0.05). In conclusion, prophylactic use of prazosin after herniorrhaphy significantly reduced the incidence of urinary retention and catheterization.

Alpha1L-adrenoceptor mediation of smooth muscle contraction in rabbit bladder neck: a model for lower urinary tract tissues of man

1. The alpha1-adrenoceptor population mediating contractile responses to noradrenaline (NA) in smooth muscles of the bladder neck from rabbit (RBN) has been characterized by use of quantitative receptor pharmacology. 2. Experiments with several 'key' alpha1-adrenoceptor antagonists of varying subtype selectivities (RS-17053, BMY 7378, indoramin, 5-methylurapidil, prazosin, REC 15/2739, SNAP 5089, terazosin, WB 4101, tamsulosin, (+)-cyclazosin and RS-100329) were conducted. Schild regression analyses yielded affinity (mean pKb) estimates of 7.1, 6.2, 8.6, 8.6, 8.4, 9.3, 7.0, 7.4, 8.9, 10.0, 7.1 and 9.3, respectively, although deviations from unit Schild regression slope question the robustness of data for RS-17053 and SNAP 5089. 3. The nature of antagonism by these agents and the profile of affinity determinations generated together suggest that a single alpha1-adrenoceptor subtype mediates contractile responses of RBN to NA. Additional studies with phenylephrine indicated also an agonist-independence of this profile. Pharmacologically, this profile was reminiscent of that described as 'alpha1L'-adrenoceptor, which has been shown to mediate contractions of several tissues including lower urinary tract (LUT) tissues of man. Furthermore, a similarity was noticed between the 'alpha1L'-adrenoceptor described here in RBN and the rabbit and human cloned alpha1a-adrenoceptor (based on data from both whole cell radioligand binding at 37 degrees C and [3H]-inositol phosphates accumulation assays), characterizations of which have been published elsewhere. 4. In conclusion, the RBN appears to provide a predictive pharmacological assay for the study of NA-induced smooth muscle contraction in LUT tissues of man.

Alpha1-adrenoceptors in testosterone-induced prostatic hypertrophy

Modifications of rat prostatic alpha1-adrenoceptors were investigated in testosterone-induced prostatic hypertrophy. [3H]prazosin bound to a single class of binding sites with a dissociation constant of 57.9+/-5.02 pM. The greater part of the binding capacity (24.6+/-1.02 fmol/mg protein) was made up of chloroethylclonidine-resistant binding sites that showed high-affinity for oxymetazoline and 5-methyl-urapidil, and was identified as alpha1A-adrenoceptors. The remaining chloroethylclonidine-sensitive binding sites that showed low-affinity for oxymetazoline and 5-methyl-urapidil were preferentially identified as alpha1B-adrenoceptors. mRNA for the three alpha1-adrenoceptors (alpha1a, alpha1b and alpha1d) was detected. Testosterone administration produced a 23% decrease of alpha1-adrenoceptor density, likely by an increase of prostatic glandular epithelium and a decrease in the relative proportion of smooth muscle, thus of alpha1-adrenoceptor density. The steady state level of mRNAs for alpha1-adrenoceptors was not modified by testosterone treatment. These results indicate that prostate alpha1-adrenoceptors are not affected in the prostatic hypertrophy induced by testosterone.

Neurohormonal stimulation of histamine release from neuroendocrine cells of the human adenomatous prostate

BACKGROUND

Neuroendocrine cells (NE) constitute a population of highly specialized cells in prostatic glands; histamine has never been described in these cells. This article shows the presence and the regulation of release of histamine in NE.

METHODS

In 21 prostatic adenomas, NE were identified by specific antisera against neuroendocrine markers (chromogranin-A, synaptophysin), histamine, and histidine decarboxylase (HDC); a rate HDC-cDNA probe was used to detect this enzyme by in situ hybridization.

RESULTS

Immunoreactive cells for chromogranin-A, histamine, and HDC were found among luminal epithelial glandular cells. Similar cells were also labeled with the HDC-cDNA probe. Glandular cells, isolated from prostatic adenomas, were shown to contain histamine (7-40 pmol/mg cellular protein). L(-) norepinephrine causes a time-dependent (t1/2 = 22 min) histamine release; the alpha 1-receptor antagonists WB-4101 and YM-617 specifically inhibited this release, in agreement with a mediation by alpha 1-adrenoreceptor subtype.

CONCLUSIONS

There is some evidence for the presence in prostatic adenomas of histamine-forming cells of neuroendocrine type; histamine release from these cells is under the control of alpha 1-adrenoreceptor subtype.