A comparison of the expression and contractile function of α1-adrenoceptors in seminal vesicle and vas deferens from normotensive and hypertensive rats.

Because hypertension related alterations occur in the properties of α(1)-adrenoceptor in several mammalian tissues and hypertension may impact ejaculatory function, we investigated hypertension related alterations in the functional, biochemical and molecular properties of α(1)-adrenoceptor in the rat seminal vesicle and vas deferens. Spontaneous seminal emission in male spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats was studied during the 3-day observation period. The characteristics of α(1)-adrenoceptor in the seminal vesicle and epididymal and prostatic portion of vas deferens of the two strains were determined using an isolated muscle bath, radioligand receptor binding and real-time reverse transcription-polymerase chain reaction techniques. SHRs had significantly higher serum testosterone than WKY rats. However, the daily mean number of ejaculatory plugs emitted and their dry weight in SHRs were significantly lower than those in WKY rats. Although there was no significant difference in the properties of α(1)-adrenoceptor in the prostatic portion of vas deferens between SHRs and WKY rats, the maximum contractile responses to phenylephrine, total α(1)-adrenoceptor density and expression of α(1A)-adrenoceptor mRNA were significantly higher in the seminal vesicle and epididymal portion of vas deferens of SHRs vs. WKY rats. Our data demonstrate the presence of hypertension related alterations in serum testosterone and in α(1)-adrenergic responsiveness of the rat seminal vesicle and vas deferens and suggest that ejaculatory function in SHRs does not mirror these hypertension related alterations.

Effects of age and hypertension on α1-adrenoceptors in the major source arteries of the rat bladder and penis.

α(1)-Adrenoceptors regulate blood pressure, regional vascular resistance and tissue blood flow. As aging and hypertension may impact pelvic arterial blood flow resulting in bladder and penile dysfunction, we investigated effects of age and hypertension on α(1)-adrenoceptors in the major source arteries of the rat bladder and penis. Using radioligand receptor binding, real-time reverse transcription-polymerase chain reaction (RT-PCR) and fluorescent microsphere infusion techniques, we compared 3 and 22-month-old male Fischer rats, and male normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Twenty-two-month-old rats and SHRs had significantly higher total α(1)-adrenoceptor density in the internal iliac artery and lower blood flow to the bladder and penis than 3-month-old and WKY rats, respectively. RT-PCR data showed an age and hypertension related increase in the expression of α(1B)-adrenoceptor mRNA in the internal iliac, vesical and internal pudendal arteries and a switch from α(1A) predominance in 3-month-old and WKY rats to α(1B)>α(1A) in 22-month-old rats and SHRs. Our data indicate the presence of age and hypertension related alterations in vascular α(1)-adrenoceptor subtype distribution and in blood flow to the rat bladder and penis. These findings suggest that pharmacological blockade of the vascular α(1B)-adrenoceptor, which could increase pelvic blood flow, may contribute to the improvement of bladder and penile dysfunctions in animal models for aging and hypertension.

Identification of potential therapeutic targets in hypertension-associated bladder dysfunction.

OBJECTIVE: To investigate differential gene expression profiles in the bladder of spontaneously hypertensive rat (SHR), as the underlying mechanisms involved in hypertension-associated bladder dysfunction remain to be clarified. MATERIALS AND METHODS: SHR and normotensive Wistar-Kyoto (WKY) rats were distributed initially in three groups: group 1 received doxazosin (30 mg/kg/day); group 2 received nifedipine (30 mg/kg/day); and group 3 received the vehicle orally for 4 weeks. The alterations in gene expression levels of candidate genes identified by microarray analysis with potential biological relevance were verified by real-time reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Voiding frequency was significantly higher, and mean voided volume was significantly lower in untreated SHRs than untreated WKY rats. Microarray analysis revealed that 25 of the differentially expressed genes in untreated SHRs compared to untreated WKY rats were related to G(s), G(i), G(q) and G(12/13) signalling, calcium handling, ion transport and smooth muscle-related genes. Furthermore, RT-PCR data, in accord with the microarray analysis, indicated that untreated SHRs had lower mRNA expression levels of Adcy2, Adcy3, Rgs2, Rgs3, Rgs4 and Arhgdia, and higher mRNA expression levels of Arhgef1, Arhgef11, Arhgef12, Geft, Rock1 and Rock2 than untreated WKY rats. The differential alterations in the micturition patterns and in the expression of several genes related to G-protein signalling pathway observed in SHRs were attenuated by treatment with doxazosin, but not nifedipine. CONCLUSION: Our data suggest that differential alterations in the expression of several genes related to G(s), G(q) and G(12/13) signalling pathways in the SHR bladder might be important in hypertension-associated bladder dysfunction.

Molecular mechanisms regulating urogenital expression of nitric oxide synthase in spontaneously hypertensive rats.

AIMS: Although doxazosin, but not nifedipine, can partially prevent a decrease in urogenital expression of nitric oxide synthase (NOS) in spontaneously hypertensive rats (SHRs), the mechanisms involved in the regulated expression of NOS are not known. Therefore, we identified differential gene expression profiles in SHRs to elucidate the molecular mechanisms regulating urogenital expression of NOS. MAIN METHODS: SHRs and normotensive Wistar-Kyoto (WKY) rats received doxazosin (30 mg/kg/day) or nifedipine (30 mg/kg/day) orally for 4 weeks. Microarray expression data of key transcripts were verified by real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. KEY FINDINGS: RT-PCR data, in accord with the microarray analysis, indicated that untreated SHRs had lower mRNA expression levels of cAMP responsive element binding protein 1 (Creb1) in the pelvic ganglion and vascular endothelial growth factor A (Vegfa) and kinase insert domain protein receptor (Kdr) in the penis, and higher mRNA expression levels of brain derived neurotrophic factor and neurotrophin 3 (Ntf3) in the bladder and Ntf3, Rho-kinases (Rock1 and Rock2) and caveolin 1 (Cav1) in the penis than untreated WKY rats. In SHRs, doxazosin and nifedipine caused a significant decrease in penile expression of Rock1 and Rock2, whereas the differential alterations in urogenital expression of Creb1, Vegfa, Kdr and Cav1 were attenuated by treatment with doxazosin, but not nifedipine. SIGNIFICANCE: Our data suggest that differential alterations in the expression of several genes related to pathways that mediate NOS expression in the urogenital tissues of SHRs, which can be attenuated by doxazosin treatment, may play an important role in regulating urogenital expression of NOS.

Short- and long-term effects of silodosin, a selective alpha 1A-adrenoceptor antagonist, on ejaculatory function in rats.

OBJECTIVE: To investigate the short- and long-term effects of silodosin, a selective alpha(1A)-adrenoceptor antagonist, on spontaneous seminal emission by isolated rats and on the properties of alpha(1)-adrenoceptor subtypes in the rat seminal vesicle, as silodosin produces a relatively high incidence rate of abnormal ejaculation and chronic administration of receptor antagonists causes an up-regulation in the targeted receptor. MATERIALS AND METHODS: Rats were treated with two doses (0.1 and 3 mg/kg/day) of silodosin orally for 3 or 30 days. Spontaneous seminal emission was studied during the 3-day observation period before completing treatment. The expression levels of alpha(1A), alpha(1B) and alpha(1D)-adrenoceptor mRNAs in the rat seminal vesicle and prostate were quantified by real-time reverse transcription-polymerase chain reaction using SYBR Green I. RESULTS: The administration of two doses of silodosin for 3 or 30 days caused a significant dose-dependent reduction in the number of ejaculatory plugs and in their dry weight. However, in rats receiving the low dose of silodosin the inhibitory effect of the drug on spontaneous seminal emission diminished significantly with chronic usage over time. Although short-term administration of silodosin did not affect expression levels of any alpha(1)-adrenoceptor subtype mRNAs in the rat seminal vesicle and prostate, long-term administration of silodosin caused a significant up-regulation in the mRNA expression of alpha(1A)-adrenoceptor in a tissue-dependent manner. CONCLUSION: Silodosin-induced up-regulation of alpha(1A)-adrenoceptor mRNA in the rat seminal vesicle might indicate potential differences in the inhibitory effect of this drug on ejaculatory function with chronic usage over time.

Prostate expression of endothelins and their receptors in rat growth.

Endothelins (ETs) have been shown to have mitogenic effects on prostate cells in vitro. To study a relationship between ETs and prostate growth, we investigated expression of ET-1 and ET-3 and their receptors ETA and ETB in the dorsolateral (DLP) and ventral (VP) prostate lobes of rats aged 3 weeks, 3 months, and 22 months. The weight ratio of each lobe to the body was not different at 3 weeks but increased more in the DLP than in the VP at 3 months; the ratio did not change at 22 months. The density of the major receptor ETA, measured by radio-labelled ET-1 binding to prostate membrane particulates, was highest at 3 weeks in both prostate lobes and decreased thereafter. mRNA expression levels of ETA, ETB, ET-1, and ET-3 in the DLP and ETA in the VP, as assessed by relative multiplex reverse transcription-polymerase chain reaction, were highest at 3 weeks, and no significant change was seen in mRNA expression of ET-converting enzyme-1. The highest expression of ETA and the ligands at 3 weeks, followed by dramatic growth at 3 months in the DLP, suggests a role of ETA-mediated signal transduction in prostate growth of rats and possibly of humans.

Differential effects of prazosin and naftopidil on pelvic blood flow and nitric oxide synthase levels in spontaneously hypertensive rats.

We compared the effects of two alpha(1)-adrenoceptor antagonists with different selectivity for the alpha(1)-adrenoceptor subtypes, prazosin and naftopidil, on pelvic blood flow and nitric oxide synthase (NOS) levels in the spontaneously hypertensive rat (SHR). SHRs and normotensive Wistar-Kyoto (WKY) rats were distributed initially in four groups: group 1 received prazosin, a subtype nonselective alpha(1)-adrenoceptor antagonist (2 mg/kg/day); group 2 received naftopidil, a selective alpha(1A/D)-adrenoceptor antagonist (10 mg/kg/day); group 3 received cyclazosin, a selective alpha(1B)-adrenoceptor antagonist (5 mg/kg/day); and group 4 received the vehicle orally for 4 weeks. Pelvic blood flow was determined by using a fluorescent microsphere infusion technique. Expression levels of nNOS and eNOS mRNAs in the rat genitourinary tissues were quantified by real-time reverse transcription polymerase chain reaction (RT-PCR) using SYBR Green I. The characteristics of alpha(1)-adrenoceptors in the rat iliac artery were determined by using radioligand receptor binding and real-time RT-PCR techniques. Untreated SHRs had lower blood flow to the ventral prostate, dorsolateral prostate, urinary bladder, and penis and lower mRNA expression levels of nNOS in the bladder and penis and eNOS in the penis than untreated WKY rats. Naftopidil had no significant effects on blood flow and NOS levels, whereas administration of prazosin and cyclazosin to the SHR caused a significant increase in blood flow to each tissue studied and a significant increase in expression levels of these genes. The density of total alpha(1)-adrenoceptors was significantly higher in iliac arteries of untreated SHRs than those of untreated WKY rats. RT-PCR data indicated that alpha(1B)-adrenoceptor mRNA was the significantly predominant gene transcript in iliac arteries of untreated SHRs. Our data show that prazosin, but not naftopidil, causes differential alterations in NOS levels in the SHR genitourinary tract, which could be due to increased pelvic blood flow resulting from inhibiting the vascular alpha(1B)-adrenoceptor. These findings may provide insight into the beneficial effects of subtype nonselective alpha(1)-adrenoceptor antagonists on prostate, bladder, and penile function, when used to treat symptoms of benign prostatic hyperplasia and elevated blood pressure.

Differential effects of diabetes induced by streptozotocin and that develops spontaneously on prostate growth in Bio Breeding (BB) rats.

We investigated molecular changes in the response to insulin in prostates of spontaneously developed (Bio Breeding) and streptozotocin (STZ)-induced diabetic rats that received sufficient amounts (euglycemic group), or suboptimal doses (hyperglycemic group) of insulin for 32 weeks, using Affymetrix GeneChip analysis of gene expression. Alterations in gene expression levels identified by microarray analysis, having potential biological relevance to prostate growth, were verified by real-time reverse transcription polymerase chain reaction (RT-PCR). A significant decrease in the weight of ventral prostate was observed in the hyperglycemic STZ-induced but not spontaneously developed diabetic group. Microarray analysis revealed that gene expression profiles were distinctly different in each region of the prostate, and that hyperglycemic diabetes in spontaneously developed and STZ-diabetic rats was associated with differential changes in the prostatic expression levels of 856 genes, of which 35 were related to cell growth, proliferation and death. RT-PCR data verified significant differences in the mRNA expression levels of Igfbp6, Tieg, and Clu between euglycemic and hyperglycemic groups, whereas expression levels of these genes in control and euglycemic diabetic groups were not significantly different. In ventral prostate, the mRNA expression levels of Igfbp6 and Tieg were significantly higher in the hyperglycemic STZ-induced diabetic than in the hyperglycemic spontaneously diabetic BBDP/Wor rats. Our data demonstrate that the diabetes induced by STZ in the BBDR/Wor rats affects prostate growth and the molecular response to insulin differently than that observed in BBDP/Wor rats that develop diabetes spontaneously.

Region and age dependent differences in alpha(1)-adrenergic responsiveness of rat seminal vesicle and vas deferens.

Because age dependent differences occur in the incidence of ejaculatory dysfunction with alpha(1)-adrenoceptor antagonists used to treat lower urinary tract symptoms secondary to benign prostatic hyperplasia, we investigated age related changes in the functional, biochemical and molecular properties of alpha(1)-adrenoceptor in the rat seminal vesicle and vas deferens. The characteristics of alpha(1)-adrenoceptor in the seminal vesicle and epididymal and prostatic portion of vas deferens of 3 and 22-month-old rats were determined using an isolated muscle bath, radioligand receptor binding and real-time reverse transcription-polymerase chain reaction techniques. Old rats had significantly higher body weight and lower testosterone than young rats. Although there was no significant age dependent difference in the properties of alpha(1)-adrenoceptor in the prostatic portion of vas deferens, the maximum contractile responses to phenylephrine, total alpha(1)-adrenoceptor density and mRNA expression of all 3 alpha(1)-adrenoceptor subtypes were significantly lower in the seminal vesicle and epididymal portion of vas deferens of 22 vs 3-month-old rats. Age dependent differences in the molecular, biochemical and functional properties of alpha(1)-adrenoceptors in the rat seminal vesicle and vas deferens may indicate potential differences in the response to alpha(1)-adrenoceptor antagonists with aging.

Effects of doxazosin on blood flow and mRNA expression of nitric oxide synthase in the spontaneously hypertensive rat genitourinary tract.

Hypertension may impact pelvic arterial blood flow resulting in reduction of nitric oxide synthase (NOS) levels. Although doxazosin, an alpha(1)-adrenoceptor antagonist, has been shown to improve erectile dysfunction as well as benign prostatic hyperplasia (BPH) and hypertension, it is not clear whether these improvements using doxazosin are primarily due to direct actions on the prostate, urinary bladder and penis, possibly via inhibition of vascular alpha(1)-adrenoceptors, or other sites of actions. Therefore, we investigated effects of doxazosin to the spontaneously hypertensive rat (SHR) on blood flow and NOS levels in the genitourinary tract. Four groups of rats were assessed: group 1, SHRs treated with doxazosin (30 mg/kg/day) for 4 weeks; group 2, SHRs treated with nifedipine (30 mg/kg/day) for 4 weeks; group 3, untreated SHRs; and group 4, untreated Wistar-Kyoto (WKY) rats. Blood flow to the ventral prostate, dorsolateral prostate, urinary bladder and penis was determined using a fluorescent microsphere infusion technique. Expression levels of nNOS and eNOS mRNAs were quantified by real-time RT-PCR using SYBR Green I. Blood flow to the ventral prostate, dorsolateral prostate, urinary bladder and penis was significantly lower in untreated SHRs than WKY rats. Treatment with doxazosin increased blood flow to each tissue studied in SHRs. RT-PCR data indicated that untreated SHRs had lower mRNA expression levels of nNOS in the bladder and penis and eNOS in the penis than WKY rats and that administration of doxazosin to the SHR caused an increase in expression levels of these genes, i.e., up-regulation of nNOS in the bladder and penis and eNOS in the penis. However, nifedipine had no significant effects on blood flow and NOS levels in the SHR genitourinary tract. Our data demonstrate that doxazosin treatment causes differential alterations in blood flow and NOS levels in the SHR genitourinary tract. These findings may provide insight into the beneficial effects of alpha(1)-adrenoceptor antagonists, on prostate, bladder and penile function, when used to treat symptoms of BPH and elevated blood pressure.

Regional differences in the functional and biochemical properties of endothelin receptor subtypes in the rabbit prostatic urethra.

OBJECTIVE: To examine the regional differences in the functional (pharmacological) and biochemical properties of endothelin (ET) receptors in the rabbit prostatic urethra. MATERIALS AND METHODS: The properties of ET receptors in 6-month-old male rabbit prostatic urethras were examined using isolated muscle-bath and radioligand receptor-binding techniques. Using plasma membrane suspensions, saturation and inhibition experiments with [(125)I]ET-1 and unlabelled agonists and antagonists (ET(A)-selective antagonist BQ123, and ET(B)-selective agonist sarafotoxin 6c, STX6c) were done to determine the ET receptor densities and their subtype specificities in the different regions of the urethra. RESULTS: The ETs (ET-1 and ET-3) produced significant concentration-dependent contractile responses in the smooth muscle strips from the different regions of the urethra. Although the maximum contractile responses induced by ET-1 were similar in the different regions, the maximum contractile responses induced by ET-3 were greater in the distal region than in the proximal or middle regions, suggesting that the contractile response to ET-1 is more potent than that to ET-3 in all regions, and that there are region-specific differences in the responses to ET-3 but not ET-1. Moreover, the ET-3-induced contractile response was suppressed by BQ788 (a selective antagonist of the ET(B) receptor) suggesting that the ET(B) receptor subtype contributes to the contractile responses mediated by ET-3. The ET receptors were expressed in higher concentrations in the distal than in the proximal or middle regions. BQ123 and STX6c inhibited [(125)I]ET-1 binding in all regions with high and low affinity constants, indicating the presence of both ET(A) and ET(B) receptor subtypes. The proportions of high-affinity binding sites for BQ123, representing ET(A) receptors, were approximately 68%, 63% and 42% in the proximal, middle and distal regions, respectively. By contrast, the proportions of high-affinity binding sites for STX6c, representing ET(B) receptors, were approximately 27%, 35% and 52% in the proximal, middle, and distal regions, respectively. These data indicate the presence of regional differences in the densities and subtype specificities of ET receptor subtypes, and the existence of regional differences in the rabbit prostatic urethra. CONCLUSION: The results suggest regional differences in ET(B) receptor subtypes that mediate contractile responses to ET-3, reflecting differences in the densities and specificities of the ET receptor subtypes in the rabbit prostatic urethra.

Age related changes in the functional, biochemical and molecular properties of alpha1-adrenoceptors in the rat genitourinary tract.

PURPOSE: Because age related changes occur in the properties of alpha(1)-adrenoceptor in several mammalian tissues and alpha(1)-adrenoceptor antagonists are extensively used to treat lower urinary tract symptoms secondary to benign prostatic hyperplasia, we investigated age related changes in the functional, biochemical and molecular properties of alpha(1)-adrenoceptor in the rat genitourinary tract. MATERIALS AND METHODS: The characteristics of alpha(1)-adrenoceptor in the ventral and dorsolateral prostate, and bladder base and dome of 3 and 22-month-old rats were determined using an isolated muscle bath, radioligand receptor binding and real-time reverse transcriptase-polymerase chain reaction techniques. RESULTS: Old rats had significantly higher body weight, lower testosterone, a smaller ventral prostate and a larger bladder dome than young rats. Although there was no significant age dependent difference in the properties of alpha(1)-adrenoceptor in the bladder base and dome, total alpha(1)-adrenoceptor density, mRNA expression of all 3 alpha(1)-adrenoceptor subtypes (alpha(1A), alpha(1B) and alpha(1D)) and the maximum contractile responses to phenylephrine were significantly lower in the ventral and dorsolateral prostate of 22 vs 3-month-old rats. CONCLUSIONS: Age related differences in the molecular, biochemical and functional properties of alpha(1)-adrenoceptors in the rat genitourinary tract may indicate potential differences in the response to alpha(1)-adrenoceptor antagonists with aging, ie a decrease in the therapeutic response in old vs young rats in the response to alpha(1)-adrenoceptor antagonists when used to treat lower urinary tract symptoms secondary to benign prostatic hyperplasia.

Effect of insulin treatment on tissue size of the genitourinary tract in BB rats with spontaneously developed and streptozotocin-induced diabetes.

To examine the differences between spontaneous and streptozotocin (STZ)-induced diabetes, four parallel studies were performed; three studies of diabetes-prone BB (BBDP/Wor) rats maintained for 8, 16, and 32 weeks and one study of STZ-injected diabetes-resistant BB (BBDR/Wor) rats maintained for 32 weeks. Each diabetic study has three groups of rats: a control group; a euglycemic group, which received sufficient amounts of insulin; and a hyperglycemic group, which received a suboptimal dose of insulin. The extent of tissue weight changes was generally shown to be less dramatic in the euglycemic diabetic than in the hyperglycemic diabetic rats. STZ-induced diabetes increased the bladder weight more dramatically (up to 3-fold) than did spontaneous diabetes (up to 2-fold). Furthermore, a significant decrease in the size of the adrenal gland (20%) and testis (10%) is observed only with spontaneous diabetes, whereas a significant decrease in the size of the ventral prostate (30%) is observed only with STZ-induced diabetes, although the serum testosterone levels are similar in both groups. Our data demonstrate that there are differences in the effect of insulin treatment on the tissue size of the genitourinary tract between spontaneously developed and streptozotocin-induced diabetes in BB rats.

Age-related alterations in the biochemical and functional properties of the bladder in type 2 diabetic GK rats.

Previous studies have demonstrated that experimental type 1 diabetes induced by streptozotocin causes alterations in the biochemical and functional properties of several receptor systems in the rat bladder. However, the exact mechanism involved in the pathophysiology of voiding dysfunction in type 2 diabetic patients is unknown. Because the GK rat is a widely accepted genetically determined rodent model for human type 2 diabetes, we investigated diabetes-induced changes in the bladder smooth muscle of the GK rats at several time points. Male GK rats and age-matched Wistar rats, as controls, were maintained for 4, 8, 16, and 32 weeks. Contractile responses to KCl, carbachol, ATP, and electrical field stimulation (EFS) were measured by using the isolated muscle bath techniques. Acetylcholine (ACh) release induced by EFS from bladder muscle strips was measured by using high-performance liquid chromatography coupled with a microdialysis procedure. Maximum contractile responses to carbachol and ATP, the release of ACh, and tissue sorbitol levels were similar in bladders from GK and control rats until 8 weeks of age. At 16 weeks of age, however, the contractile responses to carbachol and ATP, and tissue sorbitol levels were increased, and the EFS-induced ACh release was decreased in GK rats compared with controls. Although the maximum contractile responses to EFS were unchanged until 16 weeks of age, they were decreased in 32-week-old GK rats, compared with controls. Our data indicate the presence of age-related alterations in the biochemical and functional properties of the bladder in type 2 diabetic GK rats.

Molecular classification of doxazosin-induced alterations in the rat prostate using gene expression profiling.

We investigated molecular changes that occurred during chronic administration of doxazosin, an alpha1-adrenoceptor (AR) antagonist, using Affymetrix GeneChip analysis of gene expression. Rats were treated with doxazosin (4 mg/kg/day subcutaneously, supplemented with 4 mg/kg/day orally) for 12 weeks. Labeled cRNA was prepared and the subsequent hybridization to rat 230A arrays was performed. The alterations in gene expression levels of candidate genes identified by microarray analysis with potential biological relevance were verified by real-time reverse transcription polymerase chain reaction (RT-PCR) using SYBR Green I. Doxazosin treated rats had significantly heavier prostates compared to control rats. Microarray analysis revealed that chronic doxazosin treatment caused changes in the expression levels of 625 genes, of which 39 were related to cell death, necrosis, growth, proliferation and G-protein signalling pathways in the rat prostate. Furthermore, RT-PCR experiments, in accord with the microarray analysis, indicated that chronic doxazosin treatment caused an up-regulation in the mRNA expression level of clusterin, an antiapoptotic mediator, and epiregulin, a mitogen, in the ventral and dorsolateral prostate, respectively. These findings, that demonstrate chronic doxazosin administration causes significant changes in the expression of several hundred genes in the rat prostate, may provide insight into the long-term efficacy of alpha1-AR antagonists in the treatment of benign prostatic hyperplasia.

Doxazosin-induced up-regulation of alpha 1A-adrenoceptor mRNA in the rat lower urinary tract.

Alpha1-adrenoceptor (AR) antagonists can provide effective treatment of symptoms caused by benign prostatic hyperplasia. However, their mechanisms of action have not been fully elucidated. We previously reported that chronic administration of doxazosin causes an up-regulation in the mRNA expression of all three alpha1-AR subtypes in the rat prostate. As alpha1-AR antagonists might also affect the properties of alpha1-ARs in the lower urinary tract, we examined the effects of doxazosin (2 or 4 mg/kg daily subcutaneously, supplemented with 4 mg/kg daily orally for 8 or 12 weeks) on alpha1-AR subtype mRNAs in the rat bladder dome, bladder base, and urethra using real-time reverse transcription PCR. Rats that received the highest doses of doxazosin had significantly heavier bladder base and prostatic urethra than controls. PCR data showed that all three alpha1-AR subtypes were expressed in all tissues studied. Doxazosin treatment caused an up-regulation in the mRNA levels of alpha1A-AR in the rat bladder base and prostatic urethra, indicating that chronic doxazosin treatment may cause an alteration in the properties of alpha1A-AR subtype mRNA in these two areas. Furthermore, the heavier bladder base and prostatic urethra in the doxazosin-treated rats suggest that alpha1-AR antagonist treatment might also influence the growth process in these areas of the rat lower urinary tract.

Effects of chronic administration of doxazosin on alpha1-adrenoceptors in the rat prostate.

PURPOSE: Although the clinical efficacy of alpha1-adrenoceptor (alpha1-AR) antagonists for the treatment of benign prostatic hyperplasia is not disputed, their mechanism of action and ability to maintain long-term effectiveness have only recently been investigated. Since it is known that chronic administration of receptor antagonists causes up-regulation in the targeted receptor, we examined the effects of chronic administration of doxazosin, a nonspecific long acting alpha1-AR antagonist, on the properties of alpha1-AR subtypes in the rat prostate. MATERIALS AND METHODS: Rats were treated with doxazosin (2 or 4 mg/kg daily subcutaneously, supplemented with 4 mg/kg daily orally) for 8 or 12 weeks. Prostatic alpha1-AR properties at the protein and gene transcript levels were quantified by radioligand receptor binding and real-time reverse transcriptase-polymerase chain reaction, respectively. RESULTS: Treated rats that received the highest levels of doxazosin had significantly heavier prostates compared with age matched controls. After 12 weeks of treatment radioligand binding studies with radiolabeled alpha1-AR antagonist demonstrated no significant differences in the density of total alpha1-ARs in the prostate, whereas the results of real-time reverse transcriptase-polymerase chain reaction showed up-regulation in the mRNA expression levels of all 3 alpha1-AR subtypes (alpha1A, alpha1B and alpha1D) in the ventral and dorsolateral regions of the rat prostate. CONCLUSIONS: These data demonstrate that chronic treatment with doxazosin causes an alteration in the properties of the alpha1-AR system in the rat prostate. These findings may provide insight into the long-term effectiveness of alpha1-AR antagonists in the treatment of benign prostatic hyperplasia.

Age-related changes in the properties of the endothelin receptor system at protein and mRNA levels in the rat vas deferens.

As age-related changes occur in the properties of the endothelin (ET) receptor system in several mammalian tissues, and as there are significant amounts of functional ET receptors in the vas deferens, we investigated the age-related changes in the ET receptor system at the protein and mRNA levels in the rat vas deferens. The ET system was investigated in the vasa deferentia of 3 weeks, 3 months and 22 months old rats. ET receptors were characterized and quantified at the protein level by radioligand receptor binding, and gene transcript levels of ET-1, ET-3, ET converting enzyme-1 (ECE-1), and ET(A) and ET(B) receptor subtypes were quantified by real-time reverse transcription polymerase chain reaction (RT-PCR). The results of radioligand receptor binding assays demonstrate that there is a higher density of total ET receptors in the vas deferens of 3 weeks old rats than in 3 months and 22 months old rats, and that the predominant ET receptor is of the ET(A) subtype in all three ages. Real-time RT-PCR data show that the predominant mRNA expression of ETs and their receptors in all age groups studied are ET-1 and the ET(A) receptor subtype, respectively. Furthermore, ET-1, ET-3, ECE-1, and ET(A) and ET(B) receptor subtype mRNAs are expressed at higher levels in the 3 weeks old rats as compared with the other two age groups. These results demonstrate the presence of age-related changes in the properties of the ET receptor system at both protein and mRNA levels in the rat vas deferens.

Doxazosin treatment causes differential alterations of alpha 1-adrenoceptor subtypes in the rat kidney, heart and aorta.

We have previously demonstrated that long-term administration of doxazosin, an alpha(1)-adrenoceptor (alpha(1)-AR) antagonist, causes an up-regulation in the expression of alpha(1)-AR subtype mRNAs in the rat genitourinary tract and suggested that these changes may affect long-term effectiveness of alpha(1)-AR antagonists when used to treat the lower urinary tract symptoms of benign prostatic hyperplasia. As chronic administration of alpha(1)-AR antagonists may cause similar alterations in other tissues in which alpha(1)-ARs play a physiologic role, we examined the effects of long-term administration of doxazosin on the expression of alpha(1)-AR subtype mRNAs in several rat tissues. Rats were treated with doxazosin (4 mg/kg/day subcutaneously, supplemented with 4 mg/kg/day orally) for 12 weeks. The cDNA was prepared by reverse transcription of RNA extracted from the rat kidney, heart and aorta. alpha(1A), alpha(1B) and alpha(1D)-AR mRNA expression levels were quantified by real-time reverse transcription polymerase chain reaction. The rank order of expression levels of the alpha(1)-AR mRNAs in rat tissues were: alpha(1A)-AR, kidney > heart > aorta; alpha(1B)-AR, heart > kidney > aorta; alpha(1D)-AR, aorta > kidney = heart. Chronic administration of doxazosin caused an up-regulation in the mRNA level of alpha(1A), alpha(1B) and alpha(1D)-ARs in the rat kidney, heart and aorta, respectively. Our data demonstrate that doxazosin treatment causes differential alterations in the expression of alpha(1)-AR subtype mRNAs in different rat tissues. These findings may provide insight into the long-term effects of alpha(1)-AR antagonists in the treatment of diseases involving tissues whose function is regulated by alpha(1)-ARs.