Expression of alpha1 Receptor and Nitric Oxide Synthase in Oophorectomized and Estrogen-Supplemented Rat Bladder and Urethra

PURPOSE: To investigate the effects of estrogen on the expression of the alpha1 receptor and nitric oxide synthase (NOS) in rat urethra and bladder after oophorectomy. MATERIALS AND METHODS: Forty-five mature female Sprague-Dawley rats (aged 10-11 weeks, 235-250 g) were randomly assigned to one of three groups: control group, oophorectomy group (Opx), or oophorectomy and estradiol replacement group (Opx+ Est). The degree of expression of alpha1 receptor (alpha1A and D) and NOS (neuronal NOS [nNOS] and endothelial NOS [eNOS]) in bladder and urethral tissues was investigated by using immunohistochemical staining and Western blotting. RESULTS: In the bladder, the expression rates of alpha1 receptor (alpha1A and alpha1D) increased in the Opx group but decreased in the Opx+Est group. These changes were not statistically significant. The alpha1A and alpha1D receptor of the urethra decreased in the Opx group but increased in the Opx+Est group. These changes were not statistically significant. In the bladder and urethra, the expression rates of nNOS and eNOS significantly increased in the Opx group but decreased in the Opx+Est group (p<0.05). CONCLUSIONS: These data suggest that estrogen depletion increases NOS and alpha1 receptor expression in the rat bladder. However, these changes could be restored by estrogen replacement therapy.

Lack of evidence for regulation of cardiac P-type ATPases and MAP kinases in transgenic mice with cardiac-specific overexpression of constitutively active á1B-adrenoceptors

The regulatory function of á1B-adrenoceptors in mammalian heart homeostasis is controversial. The objective of the present study was to characterize the expression/activity of key proteins implicated in cardiac calcium handling (Na+/K+-ATPase and Ca2+-ATPases) and growth (ERK1/2, JNK1/2 and p38) in mice with cardiac-selective overexpression of constitutively active mutant á1B-adrenoceptor (CAMá1B-AR), which present a mild cardiac hypertrophy phenotype. Immunoblot assays showed that myocardial plasma membrane Ca2+-ATPase (PMCA) expression was increased by 30 percent in CAMá1B-AR mice (N = 6, P < 0.05), although there was no change in sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2) expression. Moreover, total Ca2+-ATPase activity was not modified, but a significant increase in the activity of the thapsigargin-resistant (PMCA) to thapsigargin-sensitive (SERCA) ratio was detected. Neither Na+/K+-ATPase activity nor the expression of á1 and á2 subunit isoforms was changed in CAMá1B-AR mouse hearts. Moreover, immunoblot assays did not provide evidence for an enhanced activation of the three mitogen-activated protein kinases studied in this stage of hypertrophy. Therefore, these findings indicate that chronic cardiac á1B-AR activation in vivo led to mild hypertrophy devoid of significant signs of adaptive modifications concerning primary intracellular calcium control and growth-related proteins, suggesting a minor pathophysiological role of this adrenergic receptor in mouse heart at this stage of development.

Expression and function of G-protein-coupled receptorsin the male reproductive tract

This review focuses on the expression and function of muscarinic acetylcholine receptors (mAChRs), α1-adrenoceptors and relaxin receptors in the male reproductive tract. The localization and differential expression of mAChR and α1-adrenoceptor subtypes in specific compartments of the efferent ductules, epididymis, vas deferens, seminal vesicle and prostate of various species indicate a role for these receptors in the modulation of luminal fluid composition and smooth muscle contraction, including effects on male fertility. Furthermore, the activation of mAChRs induces transactivation of the epidermal growth factor receptor (EGFR) and the Sertoli cell proliferation. The relaxin receptors are present in the testis, RXFP1 in elongated spermatids and Sertoli cells from rat, and RXFP2 in Leydig and germ cells from rat and human, suggesting a role for these receptors in the spermatogenic process. The localization of both receptors in the apical portion of epithelial cells and smooth muscle layers of the vas deferens suggests an involvement of these receptors in the contraction and regulation of secretion.

Esta revisão enfatiza a expressão e a função dos receptores muscarínicos, adrenoceptores α1 e receptores para relaxina no sistema reprodutor masculino. A expressão dos receptores muscarínicos e adrenoceptores α1 em compartimentos específicos de dúctulos eferentes, epidídimo, ductos deferentes, vesícula seminal e próstata de várias espécies indica o envolvimento destes receptores na modulação da composição do fluido luminal e na contração do músculo liso, incluindo efeitos na fertilidade masculina. Além disso, a ativação dos receptores muscarínicos leva à transativação do receptor para o fator crescimento epidermal e proliferação das células de Sertoli. Os receptores para relaxina estão presentes no testículo, RXFP1 nas espermátides alongadas e células de Sertoli de rato e RXFP2 nas células de Leydig e germinativas de ratos e humano, sugerindo o envolvimento destes receptores no processo espermatogênico. A localização de ambos os receptores na porção apical das células epiteliais e no músculo liso dos ductos deferentes de rato sugere um papel na contração e na regulação da secreção.

Phenyldiguanide activates cardiac receptors to produce responses by involving three different efferent pathways in anaesthetized rats.

The present study was undertaken to determine the afferent and efferent pathways involved in the phenyldiguanide (PDG)-induced reflex response in rats. Intravenous (iv) injection of PDG (10 microg/kg), produced hypotension, bradycardia and apnea over a period of time. Bilateral vagotomy abolished the PDG-induced reflex changes. Atropine (2 mg/kg; iv) blocked only the bradycardiac response produced by PDG, while prazosin (0.5 mg/kg; iv) blocked the hypotensive response, and bilateral vagotomy in these animals abolished the apneic response. In separate series of experiments, intrapericardial injection of lignocaine abolished the hypotensive and bradycardiac responses evoked by PDG in artificially ventilated rats. The results reveal that the PDG-induced reflex is mediated through vagal afferents originating from the heart and efferents involve three different pathways. The bradycardiac response was through the muscarinic receptors, the hypotension is mediated through alpha1 adrenoceptors and the apnea presumably through the spinal motoneurones supplying the respiratory muscles.

The left ventricular contractility of the rat heart is modulated by changes in flow and a1-adrenoceptor stimulation

Myocardial contractility depends on several mechanisms such as coronary perfusion pressure (CPP) and flow as well as on a1-adrenoceptor stimulation. Both effects occur during the sympathetic stimulation mediated by norepinephrine. Norepinephrine increases force development in the heart and produces vasoconstriction increasing arterial pressure and, in turn, CPP. The contribution of each of these factors to the increase in myocardial performance needs to be clarified. Thus, in the present study we used two protocols: in the first we measured mean arterial pressure, left ventricular pressure and rate of rise of left ventricular pressure development in anesthetized rats (N = 10) submitted to phenylephrine (PE) stimulation before and after propranolol plus atropine treatment. These observations showed that in vivo a1-adrenergic stimulation increases left ventricular-developed pressure (P<0.05) together with arterial blood pressure (P0.05). In the second protocol, we measured left ventricular isovolumic systolic pressure (ISP) and CPP in Langendorff constant flow-perfused hearts. The hearts (N = 7) were perfused with increasing flow rates under control conditions and PE or PE + nitroprusside (NP). Both CPP and ISP increased (P<0.01) as a function of flow. CPP changes were not affected by drug treatment but ISP increased (P<0.01). The largest ISP increase was obtained with PE + NP treatment (P<0.01). The results suggest that both mechanisms, i.e., direct stimulation of myocardial a1-adrenoceptors and increased flow, increased cardiac performance acting simultaneously and synergistically.

A new member of alpha 1-adrenoceptor-coupled G alpha h (transglutaminase II) family in pig heart: purification and characterization

We previously reported an identification of a 77-kDa GTP-binding protein that co-purified with the alpha 1-adrenoceptor following ternary complex formation. In the present paper, we report on the purification and characterization of this GTP-binding protein (termed G alpha h5) isolated from pig heart membranes. After solubilization of pig heart membranes with NaCl, G alpha h5 was purified by sequential chromatographies using DEAE-Cellulose, Q-Sepharose, and GTP-agarose columns. The protein displayed high-affinity GTP gamma S binding which is Mg(2+)-dependent and saturable. The relative order of affinity of nucleotide binding by G alpha h5 was GTP > GDP > ITP >> ATP > or = adenyl-5'-yl imidodiphosphate, which was similar to that observed for other heterotrimeric G-proteins involved in receptor signaling. Moreover, the G alpha h5 demonstrated transglutaminase (TGase) activity that was blocked either by EGTA or GTP gamma S. In support of these observations, the G alpha h5 was recognized by a specific antibody to G alpha h7 or TGase II, indicating a homology with G alpha h (TGase II) family. These results demonstrate that 77-kDa G alpha h5 from pig heart is an alpha 1-adrenoceptor-coupled G alpha h (TGase II) family which has species-specificity in molecular mass.