Multiple trial inhibitory avoidance acquisition and retrieval are resistant to chronic stress.

Chronic mild stress (CMS) is a widely accepted animal model relevant to depression that among other consequences, is chiefly known to induce anhedonia, often assessed as decreased preference for sucrose solution. CMS is also known to affect cognition, particularly memory tasks. In this study we have employed the multiple-trial inhibitory avoidance memory task (MTIA) to assess CMS effects on memory acquisition and retrieval. MTIA consists of repeated exposures to the unconditioned stimulus until a learning criterion is reached. Wistar rats underwent CMS for 5 weeks, and sucrose consumption was assessed once a week. At the end of CMS, animals were evaluated in the MTIA task. Overall decreased sucrose solution preference was highly variable. Further analyses showed that a subset of animals expressed resilience while another subset was sensitive to stress. CMS did not affect the number of acquisition sessions before reaching criterion or retrieval latency of MTIA task in neither sensitive nor resilient groups. Although tasks that assess learning ability in animal models relevant to depression indicate cognitive deficits, the ability to learn the association between compartment crossing and the aversive electric foot shock, which is strongly dependent on emotional aspects, was intact.

Effects of competition on acute phase proteins and lymphocyte subpopulations - oxidative stress markers in eventing horses.

The aim of the study was to evaluate markers of the acute phase response (APR) in eventing horses by measuring acute phase proteins (APP) (haptoglobin, Hp, and serum amyloid A, SAA), lysozyme, protein adducts such as pentosidine-like adducts (PENT), malondialdehyde adducts (MDA), hydroxynonenal adducts (HNE) and total advanced glycation/glycoxidation end products (AGEs), complete blood count and lymphocyte subpopulations (CD4+, CD8+ and CD21+) both at rest and at the end of an eventing competition. Blood samples were collected from eight Warmblood horses (medium age 10 ± 3) during an official national 2-day event competition at rest (R) and 10 min after the arrival of the cross-country test on the second day. Exercise caused a significant increase in red blood cell number, haemoglobin, packed cell volume, neutrophils, white blood cell and lymphocyte number; however, these values remained within the normal range. The CD4+ and CD8+ cells significantly increased, whereas the CD21+ lymphocytes decreased; a significant increase in serum SAA, lysozyme and protein carbonyl derivates was also observed. Two-day event causes significant changes in APR markers such as lysozyme, protein carbonyl derivates (HNE, AGEs, PENT) and lymphocyte subpopulations. The data support the hypothesis that 2-day event may alter significantly APR markers. Limitations of the study were the relatively small sample size and sampling time conditioned by the official regulations of the event. Therefore, further studies are needed to investigate the time required for recovery to basal values in order to define the possible effects on the immune function of the athlete horse.

Integration analysis of microRNA and mRNA expression profiles in human peripheral blood lymphocytes cultured in modeled microgravity.

We analyzed miRNA and mRNA expression profiles in human peripheral blood lymphocytes (PBLs) incubated in microgravity condition, simulated by a ground-based rotating wall vessel (RWV) bioreactor. Our results show that 42 miRNAs were differentially expressed in MMG-incubated PBLs compared with 1 g incubated ones. Among these, miR-9-5p, miR-9-3p, miR-155-5p, miR-150-3p, and miR-378-3p were the most dysregulated. To improve the detection of functional miRNA-mRNA pairs, we performed gene expression profiles on the same samples assayed for miRNA profiling and we integrated miRNA and mRNA expression data. The functional classification of miRNA-correlated genes evidenced significant enrichment in the biological processes of immune/inflammatory response, signal transduction, regulation of response to stress, regulation of programmed cell death, and regulation of cell proliferation. We identified the correlation of miR-9-3p, miR-155-5p, miR-150-3p, and miR-378-3p expression with that of genes involved in immune/inflammatory response (e.g., IFNG and IL17F), apoptosis (e.g., PDCD4 and PTEN), and cell proliferation (e.g., NKX3-1 and GADD45A). Experimental assays of cell viability and apoptosis induction validated the results obtained by bioinformatics analyses demonstrating that in human PBLs the exposure to reduced gravitational force increases the frequency of apoptosis and decreases cell proliferation.

In vitro and ex vivo pharmacodynamics of selected non-steroidal anti-inflammatory drugs in equine whole blood.

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenases (COX), and the inhibition of COX-2 rather than COX-1 can limit the onset of NSAID-related adverse effects. The pharmacodynamic properties of eltenac, naproxen, tepoxalin, SC-560 and NS 398 in healthy horses were investigated using an in vitro whole blood assay. To predict COX selectivity in clinical use, eltenac and naproxen were also studied ex vivo after intravenous administration. SC-560 acted as a selective COX-1 inhibitor, tepoxalin as a dual inhibitor with potent activity against COX-1, and NS 398 as a preferential COX-2 inhibitor. Eltenac was a preferential COX-2 inhibitor in vitro but un-selective in the ex vivo study. Naproxen maintained its non-selectivity both in vitro and ex vivo. These findings have demonstrated that in vitro studies may not accurately predict in vivo NSAID selectivity for COX and should be confirmed using an ex vivo whole blood assay.

Effects induced by exercise on lymphocyte ß-adrenergic receptors and plasma catecholamine levels in performance horses.

The effect of dynamic exercise on complete blood cell count, lymphocyte ß-adrenergic receptor and plasma catecholamine (adrenaline and noradrenaline) levels in horses performing different disciplines were investigated during rest and after exercise. Blood samples were collected from jumping horses (n=6), Arabian Endurance horses (n=6) and Standardbred trotters (n=6) before and immediately after competition. Dynamic exercise caused a significant increase in red blood cell count (Standardbred trotters: P=0.0012), haemoglobin concentration (jumping horses: P=0.001; Standardbred trotters: P=0.01), haematocrit percentage (Standardbred trotters: P=0.005), neutrophil percentage (jumping horses: P=0.0003), lymphocyte percentage (jumping horses: P=0.0003), monocyte percentage (Standardbred trotters: P=0.0008), lymphocyte ß-AR numbers (jumping horses: P=0.01; Arabian Endurance horses: P=0.016; Standardbred trotters: P=0.05), plasma adrenaline concentration (Standardbred trotters: P=0.0001) and plasma noradrenaline levels (Standardbred trotters: P=0.003). It is concluded that acute increases in plasma catecholamine concentrations depended on the exercise performed and may induce up-regulation of ß-AR in equine lymphocytes. However, the exact mechanism of ß-AR up-regulation still remains unclear.

Aclimatação de gengibre (Zingiber officinale Roscoe) e a relação com carboidratos endógenos / Acclimation of ginger (Zingiber officinale Roscoe) and its relation to endogenous carbohydrates

O objetivo deste trabalho foi determinar as variações dos teores de açúcares solúveis totais e de reserva nas diferentes fases de desenvolvimento de mudas de gengibre. Foram avaliados os parâmetros de sobrevivência, teores de açúcares solúveis totais e de reserva na fase de micropropagação, aclimatação e cultivo em campo. A sobrevivência das plantas no processo de aclimatação aos 60 dias foi de 100 por cento, enquanto que as plantas em condições de campo apresentaram um índice de sobrevivência de 80 por cento aos 60 dias de cultivo. Os teores médios de amido, no primeiro ano de cultivo, foram superiores nas plantas micropropagadas, tanto nas folhas (303,19±0,17 mgGlu gMF-1 mgGlu gMF-1) quanto nas raízes (3341,59±1,24 mgGlu gMF-1). Foram observados altos teores médios de amido nos rizomas (164,91±2,4 mgGlu gMF-1) e gemas (190,88±0,25 mgGlu gMF-1). Os teores médios de açúcares solúveis totais apresentaram um decréscimo nas plantas in vitro com valores médios de 86,56±0,55 mgGlug MF-1 e 94,26±0,40 mgGlu gMF-1 para folhas e raízes, respectivamente. Obteve-se um aumento nesses valores nas plantas aclimatadas em casa de vegetação, tanto nas folhas (168,22±0,77 mgGlu gMF-1) quanto nas raízes (189,68±0,70 mgGlu gMF-1), sendo superadas pelos teores médios de folhas e raízes das plantas cultivadas a campo, cujos valores foram 227,51±0,8 e 183,97±0,32 mgGlu gMF-1, respectivamente. No segundo ciclo de cultivo observou-se um aumento nos teores médios de amido nos rizomas, gemas e raízes, com valores de 210,87±0,85 mgGlu gMF-1 , 203,45±0,91 mgGlu gMF-1 e 201 ±0,69 mgGlu gMF-1 e um declínio nos teores médios nas folhas (41,55±0,88 mgGlu gMF-1) com uma queda gradativa até os 240 dias de cultivo. Porém, em relação à quantidade de açúcares solúveis totais as folhas apresentaram-se com teores médios altos no período inicial, com um declínio ao longo do desenvolvimento em casa de vegetação. O oposto foi verificado para as raízes (225,29±0,75 mgGlu gMF-1), rizoma (250,08±0,93 mgG...

The aim of this work was to determine the variations in total soluble sugar and starch levels during the different development stages of ginger seedlings. Survival parameters, as well as total soluble sugar and starch levels, were evaluated during micropropagation, acclimation and field cultivation phases. The survival of plants was 100 percent after 60 days of acclimation, whereas under field conditions such value was 80 percent after the same period. In the first year of cultivation, mean starch levels were higher in micropropagated plants, both in leaves (303.19 ± 0.17 mgGlu gFM-1) and in roots (3341.59 ± 1.24 mg Glu gFM-1). High mean starch levels were detected in rhizomes (164.91 ± 2.4 mg Glu gFM-1) and buds (190.88 ± 0.25 mgGlu gMF-1). The mean levels of total soluble sugars were lower in plants in vitro: 86.56 ± 0.55 mgGlu gFM-1 and 94.26 ± 0.40 mgGlu gFM-1 in leaves and roots, respectively. Higher values were obtained for plants acclimatized in greenhouse, both in leaves (168.22 ± 0.77 mgGlu gFM-1) and roots (189.68 ± 0.70 mgGlu gFM-1); these values were inferior to those detected in leaves and roots of plants grown in the field, which were 227.51 ± 0.8 and 183.97 ± 0.32 mgGlu gFM-1, respectively. In the second cultivation cycle, mean starch levels in rhizomes, buds and roots increased to 210.87 ± 0.85 mgGlu gFM-1, 203.45 ± 0.91 mgGlu gFM-1 and 201 ± 0.69 mgGlu gFM-1, respectively, whereas in leaves these values progressively decreased (41.55 ± 0.88 mgGlu gFM-1) until 240 days of cultivation. However, leaves presented high mean total soluble sugar levels in the initial period, with a posterior decline over the development in greenhouse. The opposite was observed in roots (225.29 ± 0.75 mgGlu gFM-1), rhizomes (250.08 ± 0.93 mgGlu gFM-1) and buds (225.75 ± 0.80 mgGlu gFM-1). Based on the high survival rate of acclimatized plants and the higher levels of total soluble sugars and starch in early stages of cultivation, acclimation is recommended to assure...

Pharmacological treatments and risks for the food chain.

Veterinarians play a pivotal role in public health control, in particular in the management of risks deriving from pharmacological treatments of food-producing animals. Veterinary medicinal products can represent a risk for animal health and welfare (side effects, decreased efficacy), for farmers and practitioners administering the drug, for consumers of food of animal origin (presence of residues, occurrence of antibiotic resistance) and for the environment. According to pending European guidelines, risk management starts from marketing authorisation that must be based on risk evaluation and can be denied when the risk/benefit ratio is not favourable considering the advantages for animal health and welfare and for safety of consumers. Veterinarians can prevent and control risks by using correct pharmacological criteria to choose and administer medicinal products and undertaking risk-based inspection of residues of drugs in food of animal origin. Moreover, a major tool for veterinarians to prevent and control drug-borne risk is "pharmacovigilance". Risks for the environment are usually assessed during the pre-marketing approval process, however veterinarians, as risk managers, should educate farmers about correct drug handling and disposal, and periodically verify that suggested measures are applied.

Steroid and beta-adrenergic receptor modifications in target organs of broiler chickens fed with a diet containing beta2-adrenergic agents.

The illegal use of beta2-agonists as repartitioning agents to improve production performance and carcass composition can induce changes in various organs of exposed animals. The aim of the present study was to evaluate the effects induced by dietary beta-agonists on beta-AR, AnR and GR in male broiler target organs. Fifty-four male broiler chickens (Ross 508), 26 days old, were randomly divided into three homogeneous experimental groups and fed for 21 days with a standard diet containing placebo (group 1, control), 1ppm of clenbuterol (group 2) and 1ppm of cimaterol (group 3). Tissue samples of heart, lung, brain, testicle, spleen, thymus and Bursa of Fabricius were collected post-mortem then cytosol fractions were used for AnR (testicles) and GR (spleen, thymus and Bursa of Fabricius), and membrane fractions for beta-AR (all tissues but testicles) determination by binding assays. The dietary administration of beta-adrenergic agents as repartitioning agents induced a significant decrease in AnR concentration in the testicle, in GR levels in the lymphoid tissues and in beta-AR concentrations of different target organs of male chickens. Present data confirm those observed in female chickens and suggest that in poultry the regulation exerted by adrenergic stimulation on steroid receptor concentrations produces different effects than in mammals.

Identification of functional alpha-adrenoceptor subtypes in the bovine female genital tract during different phases of the oestrous cycle.

The concentration and functionality of the alpha-adrenoceptor (alpha-AR) subtypes in the genital tract of cyclic heifers were investigated. In each tissue sample, a single class of alpha1-ARs was observed, whereas two distinct classes of alpha2-ARs were discriminated: low-affinity (LA) and high-affinity (HA) alpha2-ARs. Statistical analysis showed the presence of significantly (p < 0.05) higher concentrations of all alpha-AR subtypes in the follicle than in the corpus luteum. No significant differences were found in the ovary or myometrium between the luteal and follicular phases. In the ovary, the density of alpha1-ARs was significantly (p < 0.05) higher than that of alpha2-ARs. By contrast, there were significantly (p < 0.05) more alpha2-ARs than alpha1-ARs in the myometrium. As far as alpha2-ARs are concerned, LA alpha2-ARs were significantly (p<0.05) higher than HA alpha2-ARs in all tested tissues. Competition studies suggested that the rank order of potency of antagonists for alpha1-ARs was prazosin > phentolamine > yohimbine, whereas for alpha2-ARs the order of potency was yohimbine > or = phentolamine>prazosin. Functional assays performed on myometrium showed that noradrenaline, phenylephrine and clonidine elicited concentration-dependent contractions only in dioestrus and pro-oestrus preparations and that clonidine was more effective than phenylephrine as a contractile agent. It appeared that there were no significant modifications in alpha-AR affinity or concentration during the different stages of bovine oestrous cycle, whereas the uterine spontaneous activity and the responsiveness to alpha-adrenergic stimulation was strongly influenced by hormonal levels. The modifications of uterine contractility observed during the oestrous cycle may be related to modifications induced in the transductional mechanisms of alpha-ARs.

Characterization of alpha-adrenoceptor subtypes in smooth muscle of equine ileum.

OBJECTIVE: To determine the concentration and binding characteristics of alpha-adrenoceptor subtypes in smooth muscle cell membranes of equine ileum. SAMPLE POPULATION: Segments of longitudinal and circular smooth muscle from the ileum of 8 male and 8 female adult horses. PROCEDURE: Distribution of alpha-adrenoceptor subtypes was assessed by use of radioligand binding assays incorporating [3H]-prazosin and [3H]-rauwolscine, highly selective alpha1- and alpha2-adrenoceptor antagonists, respectively. Characterization of adrenoceptor subtypes was performed by use of binding inhibition assays. RESULTS: On the basis of binding affinity for specific radioligands, low- and high-affinity alpha1- and alpha2-adrenoceptors were detected. Concentration of low-affinity alpha2-adrenoceptors was significantly greater in male horses, compared with females. Competition studies confirmed the specificity of the radioligands used in the binding assays. Alpha1-adrenoceptors of both subtypes in male and female horses had a higher affinity for prazosin than phentolamine, whereas yohimbine did not compete with the radioligand for binding. For alpha2-adrenoceptors regardless of subtype, potency of inhibition elicited by each drug varied between sexes. In males, yohimbine was a more potent inhibitor than phentolamine, which was more potent than prazosin. In females, yohimbine was more potent than prazosin, which was more potent than phentolamine. CONCLUSIONS AND CLINICAL RELEVANCE: High- and low-affinity alpha1- and alpha2-adrenoceptors were detected in smooth muscle of equine ileum. Because alpha-adrenoceptor subtypes, particularly alpha2-adrenoceptors, are involved in the regulation of gastrointestinal tract function, characterization of these receptors may represent the basis for development of new therapeutic strategies for the control of gastrointestinal disturbances in horses.

Canine dilated cardiomyopathy: lymphocyte and cardiac alpha(1)- and beta-adrenoceptor concentrations in normal and affected great danes.

Serum catecholamine levels and myocardial and lymphocyte adrenergic receptor (AR) concentrations were measured in adult great danes affected by canine dilated cardiomyopathy (DCM) and compared to those of healthy animals. A non-homogeneous population of beta -AR, consisting of beta(1)-AR and beta(2)-AR, was observed in healthy (41 and 59%, respectively) and affected (17 and 83%, respectively) dog lymphocytes. Binding assays revealed that total beta -AR, beta(1)-AR and alpha(1)-AR were significantly downregulated (P<0.05;P<0.01;P<0. 001), both in lymphocyte and myocardial cell membranes of affected dogs. beta(2)-Adrenergic receptor concentrations were significantly reduced only in lymphocyte and right atrium cell membranes (P<0.05). Downregulation was not associated with alterations in receptor binding characteristics, as no significant differences in K(d)values were found. Mean plasma catecholamine levels were significantly higher (P<0.01) in DCM dogs (939+/-41) than in normal subjects (348+/-32), thus suggesting a sympathetic activation. The present study indicates a condition similar to that observed in human patients affected by DCM and that adrenergic receptors in canine lymphocytes reflect the fluctuation of adrenergic receptor concentrations in the myocardium.

Modifications of receptor concentrations for adrenaline, steroid hormones, prostaglandin F2alpha and gonadotropins in hypophysis and ovary of dairy cows with ovarian cysts.

Receptor concentrations for adrenaline, steroid hormones, PGF2alpha, LH and FSH were measured in the hypophysis and ovary of dairy cows with ovarian cysts and the results were compared with those of healthy animals. Significant modifications were found in all receptor concentrations, either between follicular and luteal structures or between the hypophyseal and ovarian receptorial status. The correlations between catecholaminergic and steroidal systems have already been demonstrated, particularly those existing between beta-adrenoceptors and steroid hormone receptors. Particular attention has been given to the possibility that a derangement in neurogenic inputs may be at the basis of some ovarian pathologies. The results of the present study suggest that the modifications of the ovarian and hypophyseal receptorial status of healthy and affected cows could play an important role in the pathogenesis of ovarian cysts.

Enhanced responsiveness of blood pressure to sodium intake and to angiotensin II is associated with insulin resistance in IDDM patients with microalbuminuria.

We assessed blood pressure (BP), body weight, renal hemodynamics, and insulin sensitivity (by euglycemic-hyperinsulinemic clamp) in nine normoalbuminuric and seven microalbuminuric IDDM patients after 6 days on a low-sodium diet (20 mEq) and after 6 days on a high-sodium diet (250 mEq). In microalbuminuric but not in normoalbuminuric IDDM patients, switching from a low to a high-sodium diet was associated with a significant increase in mean BP (from 92 +/- 3 to 101 +/- 4 mmHg; P < 0.001) and in body weight (2.91 +/- 0.63 vs. 1.47 +/- 0.26 kg; P < 0.05). Moreover, under high-sodium conditions, angiotensin II infusion (3 ng x kg(-1) x min(-1)) caused a greater increase in mean BP (14 +/- 2 vs. 7.4 +/- 1 mmHg; P < 0.05) and a smaller reduction in renal plasma flow (-122 +/- 29 vs. -274 +/- 41 ml x min(-1) x 1.73 m2; P < 0.05) in microalbuminuric than in normoalbuminuric IDDM patients. Under low sodium conditions, aldosterone increments after angiotensin II infusion were lower (P < 0.05) in microalbuminuric than in normoalbuminuric IDDM patients. Insulin-mediated glucose disposal was not affected by sodium dietary content, but it was lower in microalbuminuric (P < 0.05) than in normoalbuminuric IDDM patients. The salt-induced changes in mean BP were related to insulin sensitivity (r = -0.78; P < 0.001). In conclusion, in IDDM patients, microalbuminuria is associated with 1) an increased responsiveness of BP to salt intake and angiotensin II, 2) impaired modulation of renal blood flow, and 3) insulin resistance. Therefore, salt sensitivity in IDDM patients clusters with other factors that are likely to play an important role in the pathogenesis of diabetic nephropathy and its cardiovascular complications.

Differences between longitudinal and circular smooth muscle in beta-adrenergic control of motility of isolated equine ileum.

OBJECTIVE: To identify beta-adrenoceptor subtypes involved in motility inhibition of circular and longitudinal smooth muscle layers of equine ileum. SAMPLE POPULATION: Isolated strips of equine ileum circular smooth muscle and membrane preparations from circular and longitudinal muscle layers. PROCEDURE: Functional assays of circular muscle preparations and radioligand binding assays and measurements of cAMP production in smooth muscle membranes from circular and longitudinal layers. RESULTS: Selective beta-adrenergic agonists exerted inhibitory effects on circular muscle preparations. Binding studies of cell membranes indicated that the density and distribution of 3 beta-adrenoceptor subtypes did not differ between longitudinal and circular muscle layers. Measurement of cAMP production in membrane preparations of longitudinal and circular muscle after selective beta-stimulation confirmed presence of the 3 adenylate cyclase-coupled beta-adrenoceptor subtypes; however, preparations from the 2 layers had differing cAMP production efficacy. CONCLUSIONS: The data may partly explain the differing functional responses between circular and longitudinal muscle preparations. CLINICAL RELEVANCE: Findings support the important role of beta-atypical adrenoceptors in the inhibitory regulation of equine ileum motility.

Identification of beta-adrenergic receptor subtypes mediating relaxation in isolated equine ileum.

OBJECTIVE: To identify beta-adrenergic receptor subtypes in ileum smooth muscle of the horse. SAMPLE POPULATION: Isolated strips of equine longitudinal ileum smooth muscle and membrane preparations from smooth muscle of the intestinal wall. PROCEDURE: Functional assays and radioligand binding assays. RESULTS: Relaxation of ileum longitudinal smooth muscle proved to be mainly caused by stimulation of beta-atypical and beta 2-adrenergic receptors. Binding studies on cell membranes indicated that the total beta-adrenergic receptors population consists of 54% beta-atypical, 34% beta 2- and 12% beta 1-subtypes. CONCLUSIONS: The data suggest that sympathetic relaxation of equine ileum smooth muscle depends mainly on beta-atypical receptor subtypes activation, with a minor contribution by beta 2-subtypes. CLINICAL RELEVANCE: The important role of beta-atypical adrenergic receptor subtypes in the relaxation of equine ileum suggests possible clinical use of selective beta-atypical receptor agonists to control intestinal disturbances.

Evidence for functional beta-adrenoceptor subtypes in CG-5 breast cancer cell.

beta-adrenergic receptors (beta-ARs) were identified in CG-5 breast cancer cells using a radiometric assay. The total beta-AR concentration was measured using the highly potent beta-adrenergic antagonist (-)[3H]CGP 12177, and the densities of beta-AR subtypes were discriminated in the presence of highly selective unlabelled ligands (CGP 20712A and ICI 118551). Scatchard analysis revealed good linearity (r > 0.95) and Kd values (0.05-1 nM) indicated the presence of high affinity binding sites in CG-5 cell membranes. beta 2-AR concentrations (74%) were significantly (P < 0.05) higher than beta 1-AR concentrations (36%). Displacement studies indicated that tested adrenergic agonists displaced (-) [3H]CGP 12177 from its specific binding sites in the order of potency (-)isoproterenol > (+/-)clenbuterol > (-)adrenaline > (+/-)dobutamine > > (-)noradrenaline, whereas beta-adrenergic antagonists inhibited the binding in the following order of potency: (-)propranolol > > ICI 118 551 > > CGP 20712A. The functionality of beta-ARs identified in CG-5 cell membranes was demonstrated by the significant increase in cAMP production induced by different concentrations of isoproterenol vs unstimulated cells (control). The pathophysiological role of beta-ARs in breast cancer cells is still undefined, but their presence suggests the possible adrenergic regulation of some cellular activities such as proliferation and/or differentiation.

Down-regulation of beta-adrenergic receptors and up-regulation of estrogen and progesterone receptors induced in the reproductive system of female veal calves by dietary clenbuterol.

Effects induced by long-term administration of clenbuterol at anabolic dosages (20 micrograms/kg of body weight for 40 days) on beta-adrenergic receptor (beta-AR) subtypes, estrogen receptors (ER), and progesterone receptors (PgR) in the reproductive system of female veal calves were investigated. Clenbuterol treatment induced a significant (P < 0.01) down-regulation of beta-AR subtypes (beta 1-AR, beta 2-AR, myometrial high-affinity beta 2-AR, and ovarian low-affinity beta 2-AR). On the other hand, a significant (P < 0.01) increase of uterine and ovarian ER and PgR receptors was observed in treated calves. Treatment did not affect dissociation constant values of beta-AR, ER, or PgR. In similar manner, clenbuterol did not significantly modify distribution of ER and PgR in the various tissues of the genital tract. In fact, these receptors were significantly (P < 0.05) more concentrated in the uterus than in the vagina in treated and untreated calves. Data indicated that prolonged clenbuterol exposure induced homologous beta-AR down-regulation (down-regulation of its specific receptors) and heterologous ER and PgR up-regulation (up-regulation of different types of receptors, not specifically bound by clenbuterol) in the genital tract of veal calves. Modification of the receptorial status could be reasonably related to the pathologic changes observed in long-term treated calves (eg, hydrometra, dilatation of uterine glands, cystic ovaries). The increased concentrations of ER and PgR suggested the possible existence of subcellular mechanisms regulated by repeated beta-adrenergic stimulation.

Identification of beta-adrenoceptor subtypes in bovine ovarian and myometrial cell membranes.

Beta-adrenoceptor (beta-AR) concentrations were measured in the ovary and in the myometrium of 36 adult Friesian cows using a radiometric assay. The beta-AR content in both tissues was determined using the highly specific antagonist (-) [3H]CGP 12177 and the amounts of beta-AR subtypes were discriminated in the presence of highly selective unlabelled ligands (CGP 20712A, ICI 118 551, CGP 25827A). Scatchard analysis revealed a good linearity and Kd values suggested the existence of high affinity beta-adrenergic sites in the bovine genital tract. Total beta-AR concentrations in the ovary and in the myometrium were, respectively, 87 +/- 7 (SEM) and 240 +/- 27 fmol mg-1 of membrane protein. beta 2-AR concentrations were significantly higher (P < 0.01) in the ovary (66 +/- 5) and the myometrium (180 +/- 29) than those of beta 1-AR (21 +/- 4 and 60 +/- 5, respectively). Significant differences (P < 0.05) were also to be found between high affinity state beta 2-AR and low affinity beta 2-AR concentrations, but their values correlated negatively in the two different tissues. Natural and synthetic agonists inhibited (-) [3H]CGP 12177 binding to beta-AR in the following order of potency: (-)isoproterenol > (+/-)clenbuterol > or = (-)adrenaline >> >> (-)noradrenaline, whereas synthetic antagonists inhibited binding in the following order of potency: (-)propranolol >> (+/-)ICI 118 551 >> >> (+/-)CGP 20712A.