The alpha adrenergic binding properties of terazosin in the human prostate adenoma and canine brain

Hytrin loaded polydopamine-serotonin nanohybrid induces IDH2 mediated neuroprotective effect to alleviate Parkinson's disease

Parkinson's disease (PD) is the second most neurodegenerative disease caused due to synucleinopathy leads to the death of dopaminergic and serotonergic neurons. The approach to reduce synucleinopathy paves the therapeutic way in PD management. Recent studies highlight anti-Parkinsonism effect of Hytrin that regulates energy homeostasis via activation of mitochondrial redox regulator; IDH2 leading to attenuation of synucleinopathy. However, the burst release kinetics of Hytrin restricts its therapeutic potential. Therefore, we aimed to improve Hytrin release kinetics through nanocarrier mediated delivery, replenish dopamine and serotonin by formulating Hytrin loaded polydopamine serotonin nanohybrid for PD protection. Present study also explores IDH2 mediated neuroprotective action in retardation of synucleinopathy for PD prevention. Nanoformulation has shown effective neurotherapeutic potential by improving Hytrin release profile in the reduction of PD symptoms in vitro and ex vivo. The neuroprotective effect has been attributed to IDH2 induction and alpha-synuclein reduction against rotenone insults. The direct physical interaction of IDH2 and alpha-synuclein, PD hallmark has been uncovered. The study divulges that the restorative effect of our nanoformulation significantly retards the PD deficits byinducing IDH2 mediated alpha-synuclein ubiquitination and proteasomal degradation pathway.

Effects of an alpha-1d adrenoreceptor antagonist (naftopidil) on bladder dysfunction after radiotherapy in female rats

PURPOSE

Storage-phase bladder dysfunction can develop after pelvic radiotherapy. As the alpha-1d adrenoreceptor (a1d-AR) is dominant in the human detrusor, we aimed to investigate the effect of an a1d-AR antagonist on bladder dysfunction after pelvic radiotherapy in a rat model.

MATERIALS AND METHODS

Twenty-four female Wistar rats were used. Eight rats (14-15 weeks, 250-300 g) were randomized to three groups (normal reference group, radiation alone group and radiation plus naftopidil group). An 18-Gy dose of radiotherapy was applied to the radiation alone and radiation plus naftopidil groups. Naftopidil (20 mg/kg) was administered daily to the radiation plus naftopidil group. Four weeks after radiation, all rats underwent cystometry and were killed for reverse transcription polymerase chain reaction to detect mRNAs [a1d-AR, brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF)], Western blot to detect proteins (a1d-AR, extracellular-signal-regulated kinase, BDNF and VEGF) and immunohistochemistry.

RESULTS

Compared to the radiation alone group, (1) the decrease in the mRNA and protein expression of a1d-AR and VEGF was ameliorated, (2) the increase in the expression of BDNF mRNA and proteins such as extracellular-signal-regulated kinase and BDNF was suppressed, (3) submucosal thickness and vascularity on immunohistochemistry were improved, and (4) the baseline intravesical pressure and intercontraction interval in cystometry were ameliorated in the radiation plus naftopidil group.

CONCLUSION

Administration of an a1d-AR antagonist could improve storage-phase bladder dysfunction after radiotherapy not only by upregulating a1d-AR, which might decrease bladder compliance, but also by enhancing vascularity, which might protect the urinary bladder from chronic ischemic inflammation.

Measures of autonomic nervous system activity and lower urinary tract symptoms

Autonomic nervous system (ANS) activity may play an important role in the development of lower urinary tract symptoms (LUTS). Men with severe LUTS and men with mild or no LUTS completed the Valsalva maneuver, quantitative sudomotor axon reflex test, tilt-table, and deep breathing tests. There were no differences between men with severe LUTS compared to men with mild or no LUTS (all P values > 0.05). Systemic ANS tests may not be useful in detecting the underlying physiologic changes that lead to LUTS in aging men.

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.

Pharmacological characterization of isolated human prostate

PURPOSE

Human prostate contains alpha-1 adrenergic, cholinergic and nonadrenergic noncholinergic neuroreceptors. Using agonistic and antagonistic agents at these neuroreceptors we studied the resultant contractile responses in isolated human prostate.

MATERIALS AND METHODS

Human prostate tissue was obtained at prostatectomy for benign prostatic hyperplasia in 37 adult male patients. Tissues were suspended in tissue bath chambers connected to force displacement transducers. Specimens were subjected to agonist induced contractions, the first always being norepinephrine (NE). Specimens were pretreated with antagonist (adrenergic, cholinergic, nonadrenergic noncholinergic or none if control), followed by contraction with a second agonist (NE or other). Contractile tensions were recorded on a polygraph and then statistically analyzed.

RESULTS

The order of highest to lowest agonist induced tensile forces was NE, dopamine, acetylcholine, bethanechol, histamine and serotonin. Excitatory concentration EC(50) values were determined for each agonist tested. Significant differences were found between specific alpha-1 adrenergic receptor blockers (terazosin, prazosin and the experimental drug LY253352). In addition, many other agents antagonized the alpha-1 adrenergic receptor. Inhibitory concentration IC(50) values were obtained and the order of alpha-1 adrenergic antagonistic strengths from strongest to weakest was LY253352, prazosin, terazosin, ketanserin, SCH23390, diphenhydramine, DO710, dopamine, serotonin and histamine.

CONCLUSIONS

Human prostate neuroreceptors were determined to be alpha-1 adrenergic, dopaminergic, muscarinic cholinergic, 2A serotonergic and H1 histaminergic. Dopamine, serotonin, histamine and their antagonists blocked the adrenergic response, indicating possible receptor-receptor interaction. Further study of the pharmacology of human prostate would likely identify new drugs for treating patients with bladder outlet obstruction due to benign prostatic hyperplasia.

The effectiveness of terazosin, an alpha1-blocker, on bladder neck obstruction as assessed by urodynamic hydraulic energy

OBJECTIVE

To investigate the effectiveness of terazosin, an alpha1-adrenoceptor blocking agent, on bladder neck obstruction (BNO), by assessing the urodynamic hydraulic energy profile. Patients, subjects and methods The study included 17 men (mean age 60.1 years, range 24-84), comprising 11 patients with BNO (mean age 66.5 years) and six normal volunteers (mean age 48.1 years). A five-transducer microtip catheter was used to measure the pressure in the bladder and at the bladder neck, and in the membranous and bulbous urethra during voiding. All the subjects then received terazosin, 1 mg/day orally for 2 weeks, and were re-assessed.

RESULTS

The bladder neck diameter at maximum flow significantly (P < 0.02) increased in the 11 patients with BNO after treatment with terazosin. The relative hydraulic energy profiles before terazosin treatment showed the greatest hydraulic energy loss between the membranous and the bulbous urethra in the normal subjects, and between the bladder neck and the membranous urethra in the men with BNO. After terazosin treatment, the greatest energy loss was between the membranous and the bulbous urethra in men with BNO, similar to that in the normal controls, i.e. the whole profile of relative hydraulic energy became normal.

CONCLUSION

Terazosin was effective in opening the bladder neck and improving the hydraulic energy profile in men with BNO.

The medical management of lower urinary tract symptoms and benign prostatic hyperplasia

Prostatism is a widely used term assigned to the symptom complex of older men with voiding dysfunction. The cause of the syndrome has routinely been ascribed to an enlarged prostate. More recent thinking recognizes that many men with such symptoms do not, in fact, have prostate enlargement or benign prostatic hyperplasia (BPH) and that such symptoms are not a surrogate for BPH. Such recognition is essential if cost effective medical management of lower urinary tract symptoms (LUTS) is to be achieved. Prostate volume has emerged as a key factor in the selection of medical therapy of LUTS and BPH not only regarding symptom relief but also to the newer concept of the prevention of disease progression and the avoidance of future adverse events in those men with true BPH. In the United States, medical management is now first line therapy for LUTS. The proper selection of therapy based on the patient's individual pathophysiologic characteristics is now made possible by many new recent studies within the medical literature.

The alpha-adrenoceptor antagonist properties of the enantiomers of doxazosin in the human prostate

The alpha-adrenoceptor antagonist properties of doxazosin and its enantiomers were characterized using human prostate tissue and cell membranes isolated from rat-1 fibroblast expressing each of the cloned human alpha 1-adrenoceptor subtypes. In the alpha 1-adrenoceptor-binding studies on the human prostate with [3H]doxazosin and 2-{[beta-(3-[125I],4-hydroxyphenyl)ethyl]aminomethyl}-l-tetralone ([125I]HEAT), no significant differences were observed between racemic doxazosin, R-doxazosin and S-doxazosin (mean -log Ki (pKi) values were 8.60-8.63, 8.47-8.55 and 8.61-8.65, respectively), whereas the alpha 2-adrenoceptor-binding studies with [3H]rauwolscine and [3H]clonidine revealed that the alpha 2-adrenoceptor-binding affinity of S-doxazosin (pKi = 5.91-5.94) was slightly (3- or 4-fold), but significantly lower than that of R-doxazosin (pKi = 6.47-6.54). Studies in phenylephrine-contracted prostatic tissue showed no significant difference in alpha 1-adrenoceptor antagonist potency between racemic doxazosin, R-doxazosin and S-doxazosin (pA2 values were 8.43 +/- 0.28, 8.64 +/- 0.56 and 8.75 +/- 0.38, respectively). In the binding studies with cloned alpha 1-adrenoceptor subtypes using [3H]prazosin and [125I]HEAT, racemic doxazosin, R-doxazosin and S-doxazosin showed no selectivity for the alpha 1-adrenoceptor subtypes. The present study demonstrated that doxazosin and its enantiomers are highly selective alpha 1-adrenoceptor antagonists and that there is no evidence suggesting differential alpha 1-adrenoceptor antagonist effects of doxazosin and its enantiomers in the human prostate. Doxazosin, therefore, could be described as displaying balanced activity across all three alpha 1-adrenoceptor subtypes.

Long-term efficacy and safety of terazosin in patients with benign prostatic hyperplasia. Terazosin Research Group

OBJECTIVES

To evaluate long-term efficacy and safety of terazosin, a selective alpha 1 blocker, in the treatment of benign prostatic hyperplasia (BPH).

METHODS

This was a long-term (42 months), open-label, multicenter study with patients evaluated at 1- to 6-month intervals. Twenty-three outpatient clinics throughout the United States and Canada participated in the study. A total of 494 men with symptomatic BPH, lacking absolute indications for surgery, were enrolled in this study; 298 were transferred into the study from randomized, placebo-controlled studies of terazosin and 196 had no prior terazosin therapy. Terazosin was given starting at 1 mg/d and titrated upward until symptoms were relieved or a maximum dose of 20 mg/d was achieved, whichever came first.

RESULTS

Peak urinary flow rates at all visits were significantly higher than baseline values, with mean improvements ranging from 1.0 to 4.0 mL/s. At 3 months, 40% of patients exhibited a 30% or greater improvement in peak flow rate; this improvement was maintained through 42 months. Boyarsky symptom scores improved significantly at all visits; mean total score improved by at least 4.0 points (40%) at all visits beyond 3 months. The most common adverse events resulting in premature termination from the study were dizziness (6.7%), asthenia (3.8%), and somnolence (2.0%).

CONCLUSIONS

This study suggests that terazosin is well tolerated and effective in longterm treatment of patients with BPH.

High-affinity specific [3H]tamsulosin binding to alpha 1-adrenoceptors in human prostates with benign prostatic hypertrophy

The binding of a novel radioligand, [3H]tamsulosin, to human prostatic membranes with benign prostatic hypertrophy (BPH) has been characterized. [3H]Tamsulosin rapidly associated with its binding sites in human prostatic membranes with BPH, and the binding reached steady state by 30 min at 25 degrees C. The rate constants for association and dissociation of [3H]tamsulosin binding were calculated to be 0.21 +/- 0.05/nM per minute and 0.01 +/- 0.004/min, respectively. The specific binding of [3H]tamsulosin in human prostatic membranes was saturable and of high affinity (Kd = 0.04 +/- 0.01 nM). The density of [3H]tamsulosin-binding sites (Bmax) was 409 +/- 28 fmol/mg protein. The Kd and Bmax values for [3H]tamsulosin binding in human prostates were significantly lower than those for [3H]prazosin binding. [3H]tamsulosin binding was remarkable for its significantly lower degree of nonspecific binding. Six alpha-adrenoceptor antagonists competed with [3H]tamsulosin for the binding sites in the rank order: tamsulosin > WB4101 > prazosin > S-(+)-isomer > naftopidil > yohimbine. The binding affinities (pKi) of these antagonists for [3H]tamsulosin binding in human prostates closely correlated with their pharmacological potencies (pA2) in prostates. In conclusion, [3H]tamsulosin selectively labels alpha 1-adrenoceptors in human prostates, and thus may become a useful radioligand for the further analysis of these receptors.

Safety assessment of terazosin in the treatment of patients with symptomatic benign prostatic hyperplasia: a combined analysis

OBJECTIVES

This study reviews and assesses the safety of terazosin for the treatment of symptomatic benign prostatic hyperplasia (BPH).

METHODS

Six placebo-controlled trials (including two unpublished series) involving 996 patients provide the database for this evaluation. Six hundred thirty-six patients received terazosin from 1 to 20 mg daily for a total of 229 patient-years of exposure to terazosin. The most common final dose of terazosin was 10 mg once daily.

RESULTS

Side effects were generally mild or moderate in severity and resolved following cessation of therapy. Side effects resulted in premature withdrawal in 9% of terazosin-treated patients and 7% of placebo-treated patients (difference not significant). Dizziness (2.0%) and headache (1.1%) were the most common symptoms leading to premature withdrawal from the studies. Although postural symptoms and dizziness were slightly more common in those terazosin-treated patients 65 or more years old compared with patients less than 65 years old, this difference was not statistically significant. Only 4 of the 636 patients (0.6%) had syncopal episodes; 2 of these occurred at initiation of terazosin therapy or at dose escalation. Minimal reductions in blood pressure were observed in normotensive patients and patients with hypertension controlled by concomitant medication, whereas patients with untreated hypertension had substantial decreases in both systolic and diastolic blood pressures. Statistically significant increases in high density lipoprotein to cholesterol ratio and reductions in total cholesterol, low density lipoprotein, and triglycerides were also seen.

CONCLUSIONS

This combined analysis suggests that terazosin can be safely administered to both normotensive and hypertensive patients with symptomatic BPH.

Comparative study on alpha 1-adrenoceptor antagonist binding in human prostate and aorta

1. Specific binding of [3H]-prazosin in prostatic and aortic membranes of humans was saturable and of high affinity (prostate: apparent dissociation constant, Kd = 0.35 +/- 0.03 nmol/L; aorta: Kd = 0.26 +/- 0.03 nmol/L). The density of [3H]-prazosin binding sites (Bmax) for prostate and aorta was 546 +/- 31 and 61.6 +/- 1.6 fmol/mg protein, respectively. 2. Prazosin, YM617, naftopidil and urapidil competed with [3H]-prazosin for the binding sites in a dose-dependent manner in the prostate and aorta of humans. The binding affinities of these antagonists in both tissues were compared, based on the inhibition constant, Ki. Both prazosin and urapidil showed similar affinity to [3H]-prazosin binding sites in human tissue, whereas YM617 and naftopidil showed approximately a 12 and two times higher affinity, respectively, to alpha 1-adrenoceptor sites of prostate than aorta. 3. The chloroethylclonidine treatment reduced partially the Bmax values for specific [3H]-prazosin binding in the prostate and aorta of humans with little effect on the Kd values. 4. These data suggest that YM617 is a relatively selective antagonist of human prostatic alpha 1-adrenoceptors.

Alpha 1-adrenoceptors in human prostate: characterization and binding characteristics of alpha 1-antagonists

The role of alpha 1-adrenoceptors in the mediation of autonomic functions, particularly in the control of the cardiovascular system, is widely known. It has been shown that alpha 1-adrenoceptors localized in human prostate mediate the contraction of prostatic smooth muscles which produces an increase in the intraurethral pressure and thus, these receptors are important in the regulation of bladder outlet resistance. Alpha 1-antagonists such as prazosin relieve the symptoms of bladder outlet obstruction in men with symptomatic benign prostatic hypertrophy (BPH) by blocking alpha 1-adrenoceptors, thereby decreasing prostatic tone and urethral resistance. Thus, alpha 1-adrenergic stimulation may be one of the most important factors in the development of urinary obstruction in BPH. Alpha 1-adrenoceptors in human prostate have been identified and characterized extensively by functional, radioligand binding and molecular biological techniques. These studies provide evidence in support of the concept that the alpha 1C-subtype forms the majority of alpha 1-adrenoceptors in human prostatic smooth muscles. It has been shown that YM617 (tamsulosin) and naftopidil have higher affinities to alpha 1-adrenoceptors in the prostate than in the aorta. Some alpha 1-antagonists, such as prazosin and terazosin, are not selective with respect to alpha 1-adrenoceptor subtypes, while others, such as 5-methylurapidil and indoramin, show higher potencies for alpha 1C-adrenoceptors and much lower potencies for alpha 1A- and alpha 1B-subtypes. In conclusion, the recent findings from pharmacological and molecular biological studies indicate that selective antagonists of alpha 1C-adrenoceptors could be effective in the treatment of urinary obstruction in symptomatic BPH with fewer cardiovascular side effects.

Terazosin. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in benign prostatic hyperplasia

Terazosin selectively antagonises alpha 1-adrenoceptor-mediated contraction of the prostate, prostatic capsule, proximal urethra and bladder base, and consequently reduces urethral pressure, bladder outlet resistance and urinary symptoms associated with symptomatic benign prostatic hyperplasia. The efficacy of terazosin is reflected in increases in peak urinary flow rate, and reductions in obstructive and irritative symptom scores compared with placebo, and reductions in residual urinary volume from baseline. Clinical improvements begin to occur within 2 weeks and have been sustained for up to 2 years. The most marked treatment effects tend to occur in patients with more severe pretreatment urinary flow abnormalities. The relatively long duration of action of terazosin, allowing once-daily administration, offers a potential clinical advantage over other alpha 1-adrenoceptor antagonists although formal compliance studies have not been reported. Terazosin is generally well tolerated, but caution is recommended at treatment initiation and when dosage adjustments are made due to an increased risk of postural hypotension and related adverse effects at these times; such a risk has also been observed with several other alpha 1-adrenoceptor antagonists. Although publication of clinical trial results with terazosin is still evolving, this drug shows promise in the treatment of patients with mild to moderate symptomatic benign prostatic hyperplasia for whom surgery is not absolutely indicated. Terazosin also shows promise as a nonsurgical treatment alternative in patients with severe symptoms who are unfit for surgery and also in those who are on long waiting lists for surgery.

Terazosin in the treatment of benign prostatic hyperplasia: the United States experience

The rationale for selective alpha 1 blockade in benign prostatic hyperplasia (BPH) is based upon the observations that the prostate adenoma contains between 20% and 40% smooth muscle and the contractile properties of prostatic smooth muscle are mediated by the alpha 1 adrenoceptor. Terazosin is a selective alpha 1 adrenoceptor antagonist that is currently under clinical investigation for the treatment of clinical BPH. The United States experience with this drug is reviewed in the present report. The outcome measures used to assess the efficacy of terazosin in BPH includes Boyarsky symptom scores and uroflowmetry. The total Boyarsky symptom score decreased 55% and the peak urinary flow increased 47% following terazosin therapy in the cumulative open-label and single-blind studies. Three hundred and thirteen subjects with clinical BPH were randomised into a phase III double-blind parallel-group 3-month placebo-controlled study of once-a-day administration of terazosin. The total Boyarsky symptom score decreased 43% and 21% in the 10 mg and placebo treatment groups, respectively. The peak urinary flow increased 37% and 12% in the 10 mg and placebo-treated groups, respectively. The adverse events associated with terazosin were relatively minor and reversible. The United States experience has unequivocally demonstrated the short-term safety and efficacy of terazosin therapy in BPH. Studies are currently under way to determine the long-term safety and efficacy associated with terazosin therapy in BPH.

Alpha 1-adrenoceptor properties of terazosin HCl and its enantiomers in the human prostate and canine brain

The objective of the present study was to characterize the alpha 1-adrenoceptor binding properties of terazosin and its enantiomers in human prostate and canine brain. Human prostate adenomas were obtained from 7 males undergoing prostatectomy for symptomatic BPH and canine cerebral cortices were obtained from 6 male beagles. Competitive displacement experiments were carried out on these tissue homogenates in the presence of a constant concentration ([180 pM]) of 125I-Heat and varying concentrations of unlabelled terazosin and its enantiomers. The Ki of terazosin and its enantiomers were determined from these binding studies. The mean Ki of rac-terazosin, R(+)-terazosin, and S(-)-terazosin in human prostate was 3.6 nM, 3.8 nM, and 2.8 nM, respectively. The differences between these mean Ki values were not statistically significant. The mean Ki of rac-terazosin, R(+)-terazosin, and S(-)-terazosin in canine brain were 6.7 nM, 8.4 nM, and 5.6 nM, respectively. The differences between these mean Ki values were not significantly different. The mean Ki of terazosin and its enantiomers were consistently lower in the human prostate compared to canine brain (P less than 0.05). The present study does not provide any evidence suggesting differential effects of terazosin enantiomers on the human prostate. The twofold difference between the Ki values in the prostate and brain suggests that different subtypes of the alpha 1-receptor might be present in these tissues.

[3H]bunazosin, a novel selective radioligand of alpha 1 adrenoceptors in human prostates

The binding properties of a new radioligand, [3H]bunazosin, were studied in membranes of human prostates with benign prostatic hypertrophy (BPH). Specific binding of [3H]bunazosin was saturable, reversible, and of high affinity (Kd = 0.55 +/- 0.04 nM). The density of [3H]bunazosin binding sites (Bmax) was 676 +/- 33 fmol/mg. protein. [3H]Bunazosin rapidly associated with its binding sites in membranes of human prostates and reached steady state by 20 min. at 25C. The rate constants for association and dissociation of [3H]bunazosin binding were calculated to be 0.11 +/- 0.01/nM/min. and 0.05 +/- 0.02/min. (n = 4), respectively. Seven alpha 1 adrenoceptor antagonists competed with [3H]bunazosin for the binding sites in the rank order: R-(-)-YM-12617 greater than prazosin greater than SGB-1534 greater than bunazosin greater than terazosin greater than naftopidil greater than urapidil. In parallel studies with [3H]bunazosin, the Kd and Bmax values for [3H]prazosin binding in human prostates were slightly lower. There was a similarity in the potency and rank order of seven alpha 1, adrenoceptor antagonists for the inhibition of [3H] bunazosin and [3H]prazosin binding in human prostates. The new [3H]bunazosin binding assay in human prostates is remarkable for its low degree of nonspecific binding as compared to [3H]prazosin, especially at high ligand concentrations. Thus, [3H]bunazosin may become a useful radioligand for the further analysis of the alph 1 adrenoceptor binding sites in human prostates.

Determination of norepinephrine levels in the adult human prostate

Tissue levels of norepinephrine were measured in prostate tissue from 24 men ranging in age between 41 and 83 years. Prostatic tissue was obtained from men with subtle palpable prostate nodules undergoing transperineal needle biopsy. None of the patients were shown to have histologic evidence of adenocarcinoma. The severity of the symptoms of prostatism was evaluated prospectively using a standardized micturition symptom score questionnaire. Norepinephrine levels were quantified using a sensitive radioenzymatic assay (REA). Overall, the prostates contained relatively high levels of norepinephrine (1666 +/- 124 ng./gm.). Inverse correlations were observed between tissue norepinephrine levels and severity of symptoms of prostatism (r = -0.58; p = 0.003); age (r = -0.53; p = .008); and prostate size (r = -0.48; p = .02). Norepinephrine levels were also measured in tissue specimens obtained from men undergoing enucleation prostatectomy and transurethral resection of the prostate (TURP). The level of norepinephrine in these prostatectomy specimens (115 ng./gm.) was only 14% the level of the prostate biopsy specimens. The relatively low level of norepinephrine in the specimens obtained from patients with symptoms necessitating prostatectomy provides further evidence that norepinephrine levels are inversely related to the degree of symptomatic bladder outlet obstruction.

Use of an alpha 1-blocker, YM617, in the treatment of benign prostatic hypertrophy. YM617 Clinical Study Group

A recently synthesized alpha 1-blocker, (R)(-)-5-[2-[[2-(o-ethoxyphenoxy)ethyl]amino]propyl]-2- methoxybenzenesulfonamide hydrochloride (YM617), was evaluated in 270 patients with benign prostatic hypertrophy in a double-blind study. After 2 weeks on placebo the patients were assigned at random to 4 groups: group P--placebo, group L--0.1 mg., group M--0.2 mg. and group H--0.4 mg. of YM617. Comparing the placebo to the treatment period, subjective symptoms, such as nocturia and urgency, were significantly decreased in group H (p less than 0.01). The sensation of incomplete voiding was significantly improved in groups M and H (p less than 0.01). However, the differences among the groups were statistically insignificant. Residual urine volume was significantly decreased in groups L, M and H after instillation of saline into the bladder (p less than 0.01) but not in group P. The maximum and average flow rates were significantly increased in groups L, M and H (p less than 0.01) but not in group P. Average flow rate showed significant differences between groups M or H versus group P. Neither orthostatic hypotension nor a decrease in blood pressure was noted. Adverse side effects and changes in laboratory data were all slight and disappeared when the second tests were performed. In summary, the irritative and obstructive symptoms caused by benign prostatic hypertrophy were decreased and urodynamic studies were markedly improved by the alpha 1-blocker, YM617. The drug seems to be useful in the treatment of patients with benign prostatic hypertrophy.

Density and localization of alpha 1-adrenoceptors in hypertrophied prostate

Alpha-adrenoceptors have been considered to play an important role in the regulation of the voiding force. In order to determine the density and localization of the alpha-adrenoceptors in the prostate, binding assays for alpha-adrenoceptors were performed with [3H]prazosin and [3H] yohimbine in membrane preparations from enucleated hyperplastic prostate tissues. Furthermore, autoradiographic analysis of alpha-adrenoceptors in the sliced tissue specimens from benign prostatic hypertrophy was performed. Specific binding of both ligands were saturable and of high affinity in membrane preparations, and Scatchard analyses indicated Bmax = 104 fmole/mg. protein, Kd = 0.488 nM for [3H]prazosin, and Bmax = 41 fmole/mg, protein, Kd = 1.83 nM for [3H] yohimbine. Bmax and Kd for [3H]prazosin were greater in the adenoma than in the submucosal tissue of the prostatic urethra. No relationship was noted between the size of enucleated prostate and the density of alpha-adrenoceptors. Image analysis of autoradiograms using [3H]prazosin showed specific binding sites could not be clearly demonstrated, but only [125I]HEAT slightly exposed specific binding sites in the prostate.

Binding and functional properties of doxazosin in the human prostate adenoma and canine brain

The binding and functional properties of doxazosin were characterized in the canine brain and human prostate. 3H-Doxazosin binding sites were characterized in canine brain and human prostate homogenates using saturation experiments. The binding of 3H-doxazosin in the canine brain was consistently saturable and of high affinity. The mean equilibrium dissociation constant (Kd) and density (Bmax) of 3H-doxazosin binding sites in the canine brain were 0.19 nM and 2.17 fmol/mg wet wt, respectively. The binding of 3H-doxazosin in human prostate homogenates was not consistently linear owing to a relatively high proportion of nonspecific doxazosin binding sites. The mean Kd and Bmax of 3H-doxazosin binding sites in the prostate determined from the saturation experiments yielding linear Scatchard plots were 0.2 nM and 0.51 fmol/mg wet wt. The pharmacology of doxazosin binding sites was further characterized in the canine brain using competitive binding experiments. The rank order of IC50corr values for norepinephrine, clonidine, yohimbine, terazosin, and prazosin indicated that doxazosin binds selectively to alpha 1 and alpha 2 adrenergic binding sites. The relative affinity of unlabeled doxazosin for alpha 1 and alpha 2 binding sites in the human prostate was determined by displacing 125I-Heat or 3H-rauwolscine with varying concentrations of unlabeled doxazosin. The affinity of doxazosin for alpha 1 binding sites in the prostate adenoma was approximately 100-fold greater than its affinity for alpha 2 binding sites. The potency of doxazosin for inhibiting phenylephrine-induced contractions in the prostate indicated that prostate smooth muscle contraction is mediated by alpha 1 adrenoceptors.

Role of alpha-adrenergic blockers in the treatment of benign prostatic hyperplasia

The dynamic component of infravesical obstruction in men with symptomatic benign prostatic hyperplasia (BPH) is determined by alpha 1-adrenoceptor-mediated contractions of the prostatic capsule, prostate adenoma, and bladder neck. Since alpha 1-adrenoceptors are sparse in the bladder, medical therapy aimed at blocking the alpha receptor will relieve bladder outlet obstruction without inhibiting bladder function. Numerous clinical studies have evaluated the use of various alpha blockers for the treatment of BPH. Although the majority of these trials involved limited numbers of patients treated for only short periods, their results have consistently shown that alpha blockers improve urinary flow rates. Adverse reactions appear to be more frequent and more serious with the use of nonselective alpha blockers than with selective alpha 1 blockers, such as terazosin or prazosin. Terazosin offers the additional advantage of once-daily dosing. The common association of hypertension, hyperlipidemia, and symptomatic BPH in the aging male population may provide further impetus for initiating treatment with alpha blockers because alpha blockers are effective antihypertensive agents and may favorably alter lipid profiles.