RESUMO
Fish can change their skin and eye colour for background matching and signalling. Males of Gasterosteus aculeatus develop ornamental blue eyes and a red jaw during the reproductive season, colours that are further enhanced during courtship. Here, the effects of different hormones on physiological colour changes in the eyes and jaws of male and female G. aculeatus were investigated in vitro. In an in vivo experiment, G. aculeatus were injected with a receptor blocker of a pivotal hormone (noradrenaline) that controls colour change. In males, noradrenaline had aggregating effects on melanophore and erythrophore pigments resulting in blue eyes and a pale jaw, whereas melanocyte-concentrating hormone (MCH) and melatonin resulted in a pale jaw only. When noradrenalin was combined with melanocyte stimulating hormone (MSH) or prolactin, the jaw became red, while the eyes remained blue. In vivo injection of yohimbine, an alpha-2 adrenoreceptor blocker, resulted in dispersion of melanophore pigment in the eyes and inhibited the blue colouration. Altogether, the data suggest that noradrenalin has a pivotal role in the short-term enhancement of the ornamental colouration of male G. aculeatus, potentially together with MSH or prolactin. This study also found a sex difference in the response to MCH, prolactin and melatonin, which may result from different appearance strategies in males, versus the more cryptic females.
Assuntos
Cromatóforos/metabolismo , Cor de Olho , Pigmentos Biológicos/metabolismo , Pigmentação da Pele , Smegmamorpha/metabolismo , Animais , Olho , Feminino , Masculino , Hormônios Estimuladores de Melanócitos/metabolismo , Melatonina/metabolismo , Norepinefrina/metabolismo , ReproduçãoRESUMO
Immunohistochemical techniques were employed to investigate the distribution of amylin-like immunoreactivity in the axolotl (Ambystoma mexicanum) pituitary. Amylin-immunoreactive cells were observed in the pars intermedia, and these cells were found to be immunoreactive for α-melanocyte-stimulating hormone (αMSH) as well. In contrast, αMSH-immunoreactive cells in the pars distalis were immuno-negaitive for amylin. These light microscopic findings were confirmed by immunoelectron microscopy. Amylin-immunoreactive signals were located on the haloes of presumable secretory granules in association with αMSH-immunoreactive signals in the amylin-positive cells. However, in the pars distalis, the αMSH-positive cells did not contain amylin-immunoreactive secretory granules. Western blot analysis of axolotl pituitary extracts revealed the labeling of a protein band at approximately 10.5-kDa by the anti-rat amylin serum, which was not labeled by the anti-αMSH antibody. These findings indicate that amylin secreted from MSH-producing cells in the pars intermedia may modulate MSH secretion in an autocrine fashion and may participate in MSH functions such as fatty homeostasis together with MSH.
Assuntos
Ambystoma mexicanum/anatomia & histologia , Adeno-Hipófise/citologia , Adeno-Hipófise Parte Intermédia/citologia , Proteínas de Anfíbios/metabolismo , Animais , Forma Celular , Imuno-Histoquímica , Hormônios Estimuladores de Melanócitos/metabolismoRESUMO
It is well known that endocannabinoids play an important role in the regulation of food intake and body weight. Endocannabinoids and cannabinoid receptors are found in the hypothalamus and brainstem, which are central areas involved in the control of food intake and energy expenditure. Activation of these areas is related to hypophagia observed during inflammatory stimulus. This study investigated the effects of cannabinoid (CB1) receptor blockade on lipopolysaccharide (LPS)-induced hypophagia. Male Wistar rats were pretreated with rimonabant (10 mg/kg, by gavage) or vehicle; 30 min later they received an injection of either LPS (100 µg/kg, intraperitoneal) or saline. Food intake, body weight, corticosterone response, CRF and CART mRNA expression, Fos-CRF and Fos-α-MSH immunoreactivity in the hypothalamus and Fos-tyrosine hydroxylase (TH) immunoreactivity in the brainstem were evaluated. LPS administration decreased food intake and body weight gain and increased plasma corticosterone levels and CRF mRNA expression in the PVN. We also observed an increase in Fos-CRF and Fos-TH double-labeled neurons after LPS injection in vehicle-pretreated rats, with no changes in CART mRNA or Fos-α-MSH immunoreactive neurons in the ARC. In saline-treated animals, rimonabant pretreatment decreased food intake and body weight gain but did not modify hormone response or Fos expression in the hypothalamus and brainstem compared with vehicle-pretreated rats. Rimonabant pretreatment potentiated LPS-induced hypophagia, body weight loss and Fos-CRF and Fos-TH expressing neurons. Rimonabant did not modify corticosterone, CRF mRNA or Fos-α-MSH responses in rats treated with LPS. These data suggest that the endocannabinoid system, mediated by CB1 receptors, modulates hypothalamic and brainstem circuitry underlying the hypophagic effect during endotoxemia to prevent an exaggerated food intake decrease. This article is part of a Special Issue entitled 'Central Control of Food Intake'.
Assuntos
Anorexia Nervosa/patologia , Tronco Encefálico/patologia , Hormônio Liberador da Corticotropina/metabolismo , Hipotálamo/patologia , Neurônios/enzimologia , Receptor CB1 de Canabinoide/antagonistas & inibidores , Tirosina 3-Mono-Oxigenase/metabolismo , Animais , Anorexia Nervosa/etiologia , Peso Corporal/efeitos dos fármacos , Contagem de Células , Corticosterona/sangue , Hormônio Liberador da Corticotropina/genética , Modelos Animais de Doenças , Ingestão de Alimentos/efeitos dos fármacos , Endotoxemia/induzido quimicamente , Endotoxemia/complicações , Regulação da Expressão Gênica/efeitos dos fármacos , Hipotálamo/efeitos dos fármacos , Lipopolissacarídeos/toxicidade , Masculino , Hormônios Estimuladores de Melanócitos/genética , Hormônios Estimuladores de Melanócitos/metabolismo , Microdiálise , Neurônios/efeitos dos fármacos , Proteínas Oncogênicas v-fos/genética , Proteínas Oncogênicas v-fos/metabolismo , Piperidinas/farmacologia , Pirazóis/farmacologia , RNA Mensageiro/metabolismo , Radioimunoensaio , Ratos , Ratos Wistar , Rimonabanto , Fatores de TempoRESUMO
Parkinson's disease is a neurodegenerative process characterized by progressive degeneration of the substantia nigra and concurrent loss of neuromelanin in these structures. The present hypothesis suggests that progression of Parkinson's disease may be reduced by enhancing the regional levels of neuroprotective factors derived from proopiomelanocortin (POMC). One practical means to accomplish this goal may be administration of ketoconazole or other inhibitors of corticosteroid synthesis at doses sufficient to stimulate hypophyseal secretion of POMC. The POMC constituents adrenocorticotropic hormone (ACTH) and melanocycle-stimulating hormone (MSH), which mobilize neuromelanin generation and lipotropins, those motivating lipid components of neuromelanin and endorphin, which then together stimulate and protect neural components of the substantia nigra.
Assuntos
Cetoconazol/farmacologia , Doença de Parkinson/tratamento farmacológico , Pró-Opiomelanocortina/genética , Corticosteroides/antagonistas & inibidores , Hormônio Adrenocorticotrópico/metabolismo , Humanos , Cetoconazol/uso terapêutico , Melaninas/metabolismo , Hormônios Estimuladores de Melanócitos/metabolismo , Doença de Parkinson/genética , Doença de Parkinson/metabolismo , Pró-Opiomelanocortina/metabolismoRESUMO
BACKGROUND: Exposure to ultraviolet (UV) radiation induces generation of reactive oxygen species, production of proinflammatory cytokines and melanocyte-stimulating hormone (MSH) as well as increase in tyrosinase activity. The potential photoprotective effects of Coccoloba uvifera extract (CUE) were evaluated in UV-stimulated melanocytes. METHODS: Human epidermal melanocytes were used as an in vitro model to evaluate the effects of CUE on the production interleukin-1alpha (IL-1alpha), tumor necrosis factor alpha (TNF-alpha), and alpha-MSH under basal and UV-stimulated conditions. Antioxidant and anti-tyrosinase activities were also evaluated in membrane lipid peroxidation and mushroom tyrosinase assay, respectively. RESULTS: Coccoloba uvifera L. showed antioxidant and anti-tyrosinase activities and also inhibited the production of IL-1alpha, TNF-alpha and alpha-MSH in melanocytes subjected to UV radiation (P<0.01). Moreover, CUE inhibited the activity of tyrosine kinase in cell culture under basal and UV radiation conditions (P<0.001), corroborating the findings of the mushroom tyrosinase assay. CONCLUSION: This study supports the photoprotective potential of CUE.
Assuntos
Melanócitos/efeitos dos fármacos , Polygonaceae/química , Antioxidantes/farmacologia , Células Cultivadas , Inibidores Enzimáticos/farmacologia , Humanos , Hormônios Estimuladores de Melanócitos/metabolismo , Melanócitos/metabolismo , Monofenol Mono-Oxigenase/antagonistas & inibidores , Monofenol Mono-Oxigenase/metabolismo , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Proteínas Tirosina Quinases/metabolismo , Fator de Necrose Tumoral alfa/imunologiaRESUMO
Somatolactin (SL) is a pituitary hormone present exclusively in fish that is involved in different physiological processes. The role of SL was evaluated in Cichlasoma dimerus (Teleostei, Perciformes) exposed for 10 days to a black and white background (BB and WB). Changes in alpha-melanophore stimulating hormone (alphaMSH) and melanin concentrating hormone (MCH) cells were also analyzed for comparison with SL. A melanin dispersing effect was observed in fish exposed to a BB, while a concentrating one was observed in those exposed to a WB. By Western blot, three SL-immunoreactive (ir) bands (32, 28 and 23.5 kD) were evidenced. Pituitary SL-ir levels were 2.66- and 2.67-fold greater in the 32 Kd and 28 kD bands, respectively, in BB fish compared with those of WB fish. The SL-ir 23.5 Kd band was not included in the analysis because of its unknown identity. In addition, SL-ir cell number and area were significantly higher in the BB condition (BB 22.73+/-1.46, WB 7.37+/-0.54 and BB 27.39+/-1.00 microm2; WB: 16.61+/-0.65 microm2). No significant differences were observed in the number of the hypothalamic MCH-ir neurons. However, a significant difference was observed in their nuclear area (BB 11.61+/-0.42 microm2, WB 17.80+/-0.84 microm2). alphaMSH-ir cells showed a marked increased in number (BB 35.96+/-1.22, WB 24.36+/-1.04), but no significant differences were observed in the cell area. In conclusion, this study presented clear evidence towards a possible involvement of SL in the adaptation to background colors in teleost together with alphaMSH and MCH.
Assuntos
Adaptação Fisiológica , Ciclídeos/fisiologia , Meio Ambiente , Proteínas de Peixes/metabolismo , Glicoproteínas/metabolismo , Hormônios Hipofisários/metabolismo , Pigmentação da Pele/fisiologia , Pele/metabolismo , Animais , Contagem de Células , Núcleo Celular , Hormônios Hipotalâmicos/metabolismo , Hipotálamo/citologia , Hipotálamo/metabolismo , Melaninas/metabolismo , Hormônios Estimuladores de Melanócitos/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Hipófise/química , Hipófise/metabolismoRESUMO
Cabergoline or bromocriptine were administered orally to 60 bitches at doses of 5 microg/kg and 15 microg/kg daily, respectively, for two to 45 days for the treatment of pseudopregnancy or for oestrus induction. Seven of the dogs which received cabergoline for more than 14 days developed coat colour changes from the second week of administration to the next coat shedding. Of these, fawn-coloured bitches developed a yellowish coat colour while Argentine boar hounds became black spotted, mainly on their extremities. In previous untreated oestrous periods, these bitches had shown no coat colour changes. It is concluded that a colour shift in certain haircoats of particular breeds could be mediated through the inhibition of the secretion of melanocyte-stimulating hormone by the administration of the dopaminergic agonist cabergoline for more than two weeks. Transient coat colour changes should be considered a possible side effect when planning long-term treatment with dopaminergic agonists in dogs.
Assuntos
Doenças do Cão/induzido quimicamente , Agonistas de Dopamina/efeitos adversos , Ergolinas/efeitos adversos , Cor de Cabelo/efeitos dos fármacos , Pigmentação , Pseudogravidez/veterinária , Animais , Bromocriptina/uso terapêutico , Cabergolina , Cães , Agonistas de Dopamina/uso terapêutico , Ergolinas/uso terapêutico , Ciclo Estral/efeitos dos fármacos , Feminino , Hormônios Estimuladores de Melanócitos/metabolismo , Hormônios Estimuladores de Melanócitos/farmacologia , Linhagem , Pseudogravidez/tratamento farmacológicoRESUMO
Peptide secretion from rat melanotropes is tonically inhibited by a dopaminergic synaptic input that develops after birth and acts through D2 dopamine receptors. In this study, whole-cell Na(+) currents were recorded from melanotropes that were isolated from rat pituitary intermediate lobes at postnatal days 1-20 (P1-P20) and maintained in culture for 5-24 h. Coincident with the development of innervation, melanotropes exhibited a progressive decrease in peak Na(+) current density from P3 to P14. The decrease involved a 50% reduction in maximal Na(+) conductance with no detectable changes in channel gating. Subcutaneous injections of the D2 antagonist sulpiride, applied from P11 to P13, restored melanotrope Na(+) channel activity to pre-innervation levels. Thus, the activation of D2 receptors by the dopaminergic input reduces the functional expression of Na(+) channels in melanotropes.
Assuntos
Animais Recém-Nascidos/metabolismo , Dopamina/fisiologia , Hormônios Estimuladores de Melanócitos/metabolismo , Hipófise/fisiologia , Canais de Sódio/fisiologia , Envelhecimento/fisiologia , Animais , Animais Recém-Nascidos/genética , Células Cultivadas , Condutividade Elétrica , Hipófise/crescimento & desenvolvimento , Ratos , Ratos WistarRESUMO
The native hormone alpha-melanocyte-stimulating hormone (alpha-MSH) and its more potent analog [Nle(4),D-Phe(7)]alpha-MSH (NDP-alpha MSH), labeled at the amino terminal with the fluorescent aminobenzoic acid (Abz) isomers, were examined by fluorescence methods. We observed energy transfer between the tryptophan(9) residue acting as donor and Abz as acceptor, the transfer being more pronounced to the ortho-form of the acceptor. Within the hypothesis that different peptide conformations coexist in equilibrium during the fluorescence decay, we supposed that the intensity decay was modulated by an acceptor-donor distance distribution function f(r). From the time-resolved fluorescence experimental data, we recovered the distance distribution between Abz and Trp(9), using the CONTIN program, within the framework of the Förster resonance energy transfer model. The methodology proved to be useful to provide quantitative information about conformational dynamics of melanotropins and its dependency on the solvent. In aqueous medium, alpha-MSH has a broad Abz-Trp(9) distance distribution, reflecting the structural flexibility of the peptide. Three different distance populations could be identified in the labeled analog NDP-alpha MSH in water, indicating distinct conformational states for the synthetic peptide, compared with the native hormone. Measurements in trifluoroethanol resulted in the recovery of two Abz-Trp(9) distance populations, both for the native and the analog hormones, reflecting the decrease, induced by the solvent, of the conformational states available to the peptides.
Assuntos
Ácido 4-Aminobenzoico/metabolismo , Hormônios Estimuladores de Melanócitos/química , Hormônios Estimuladores de Melanócitos/metabolismo , Soluções Tampão , Transferência de Energia , Fluorescência , Conformação Proteica , Rotação , Espectrometria de Fluorescência , Fatores de TempoRESUMO
Some rat melanotrophs express in vivo tyrosine hydroxylase mRNA. In this report we show, by Western-blotting, that cultures of adult rat melanotrophs, but not adenohypophyseal cells, express tyrosine hydroxylase. Immunocytochemical analyses confirmed the existence of a subpopulation of melanotrophs expressing tyrosine hydroxylase. Bromocryptine (2.5 x 10(-7) M), a D2 dopamine agonist, down-regulated melanotroph tyrosine hydroxylase expression in a time-dependent manner; initial effect was detected at 15 h and maximum at 3 days treatment (reduction to about 40% of control values). Down-regulation at 3 days was dose-dependent (ED(50) around 2 x 10(-9) M). This decrease was reversed by sulpiride, a D2 dopamine antagonist. The cell number was slightly increased by bromocryptine treatment. These data suggest tyrosine hydroxylase expression in melanotrophs being under tonic inhibitory control by dopamine innervation in vivo.