RESUMO
Intracellular calcium levels ([Ca2+]i) and glucose uptake are central to cardiomyocyte physiology, yet connections between them have not been studied. We investigated whether insulin regulates [Ca2+]i in cultured cardiomyocytes, the participating mechanisms, and their influence on glucose uptake via SLC2 family of facilitative glucose transporter 4 (GLUT4). Primary neonatal rat cardiomyocytes were preloaded with the Ca2+ fluorescent dye fluo3-acetoxymethyl ester compound (AM) and visualized by confocal microscopy. Ca2+ transport pathways were selectively targeted by chemical and molecular inhibition. Glucose uptake was assessed using [3H]2-deoxyglucose, and surface GLUT4 levels were quantified in nonpermeabilized cardiomyocytes transfected with GLUT4-myc-enhanced green fluorescent protein. Insulin elicited a fast, two-component, transient increase in [Ca2+]i. Nifedipine and ryanodine prevented only the first component. The second one was reduced by inositol-1,4,5-trisphosphate (IP3)-receptor-selective inhibitors (xestospongin C, 2 amino-ethoxydiphenylborate), by type 2 IP3 receptor knockdown via small interfering RNA or by transfected Gßγ peptidic inhibitor ßARKct. Insulin-stimulated glucose uptake was prevented by bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid-AM, 2-amino-ethoxydiphenylborate, and ßARK-ct but not by nifedipine or ryanodine. Similarly, insulin-dependent exofacial exposure of GLUT4-myc-enhanced green fluorescent protein was inhibited by bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid-AM and xestospongin C but not by nifedipine. Phosphatidylinositol 3-kinase and Akt were also required for the second phase of Ca2+ release and GLUT4 translocation. Transfected dominant-negative phosphatidylinositol 3-kinase γ inhibited the latter. In conclusion, in primary neonatal cardiomyocytes, insulin induces an important component of Ca2+ release via IP3 receptor. This component signals to glucose uptake via GLUT4, revealing a so-far unrealized contribution of IP3-sensitive Ca2+ stores to insulin action. This pathway may influence cardiac metabolism in conditions yet to be explored in adult myocardium.
Assuntos
Transportador de Glucose Tipo 4/metabolismo , Glucose/farmacocinética , Receptores de Inositol 1,4,5-Trifosfato/fisiologia , Inositol 1,4,5-Trifosfato/fisiologia , Insulina/farmacologia , Miócitos Cardíacos/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Cálcio/metabolismo , Células Cultivadas , Glucose/metabolismo , Inositol 1,4,5-Trifosfato/metabolismo , Inositol 1,4,5-Trifosfato/farmacologia , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Miócitos Cardíacos/metabolismo , Transporte Proteico/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Regulação para Cima/efeitos dos fármacosRESUMO
The purpose of the present study was to explore changes in rat colon motility, and determine the roles of calcium and inositol (1,4,5)-triphosphate (IP3) in colon dysmotility induced by multiple organ dysfunction syndrome (MODS) caused by bacteria peritonitis. The number of stools, the contractility of the muscle strips and the length of smooth muscle cells (SMC) in the colon, the concentration of calcium and IP3 in SMC, and serum nitric oxide were measured. Number of stools, fecal weight, IP3 concentration in SMC and serum nitric oxide concentration were 0.77 +/- 0.52 pellets, 2.51 +/- 0.39 g, 4.14 +/- 2.07 pmol/tube, and 113.95 +/- 37.89 micromol/L, respectively, for the MODS group (N = 11) vs 1.54 +/- 0.64 pellets, 4.32 +/- 0.57 g, 8.19 +/- 3.11 pmol/tube, and 37.42 +/- 19.56 micromol/L for the control group (N = 20; P < 0.05). After treatment with 0.1 mM acetylcholine and 0.1 M potassium chloride, the maximum contraction stress of smooth muscle strips, the length of SMC and the changes of calcium concentration were 593 +/- 81 and 458 +/- 69 g/cm(3), 48.1 +/- 11.8 and 69.2 +/- 15.7 microM, 250 +/- 70 and 167 +/- 48%, respectively, for the control group vs 321 +/- 53 and 284 +/- 56 g/cm(3), 65.1 +/- 18.5 and 87.2 +/- 23.7 microM, 127 +/- 35 and 112 +/- 35% for the MODS group (P < 0.05). Thus, colon contractility was decreased in MODS, a result possibly related to reduced calcium concentration and IP3 in SMC.
Assuntos
Cálcio/fisiologia , Colo/fisiopatologia , Motilidade Gastrointestinal/fisiologia , Inositol 1,4,5-Trifosfato/fisiologia , Insuficiência de Múltiplos Órgãos/fisiopatologia , Miócitos de Músculo Liso/química , Animais , Cálcio/análise , Colo/citologia , Imuno-Histoquímica , Inositol 1,4,5-Trifosfato/análise , Masculino , Óxido Nítrico/sangue , Ratos , Ratos WistarRESUMO
The intense periodic calcium activity experimentally observed in the Xenopus embryo at the Mid Blastula Transition stage is closely related to the competence of the embryonic cells of the marginal zone to respond to the posterior-mesodermal inducting signals from the Fibroblast Growth Factor (FGF). In this work we do a stability analysis and study numerically an extension of a mathematical model previously introduced by us [Diaz, J., Baier, G., Martinez-Mekler, G., Pastor, N., 2002. Interaction of the IP(3)-Ca(2+) and the FGF-MAPK signaling pathways in the Xenopus laevis embryo: a qualitative approach to the mesodermal induction problem. Biophys. Chem. 97, 55-72] for the interaction of the Inositol 1,4,5-triphosphate-Calcium (IP(3)-Ca(2+)) and the Mitogen-Activated Protein Kinase (MAPK) signaling pathways at the Mid Blastula Transition stage or stage 8 of development. This allows us to consider the effect of the oscillatory calcium dynamics on the FGF input signal carried by the MAP kinase (ERK) into the nucleus. We find that this interaction of the pathways induces a limit cycle behavior for ERK with frequency-encoding characteristics. We believe that this periodic increase of the ERK levels in the nucleus is related to the ability of the cell to express posteriorizing mesodermal features induced by the FGF signal at stage 8.
Assuntos
Blastômeros/fisiologia , Cálcio/metabolismo , Inositol 1,4,5-Trifosfato/fisiologia , Sistema de Sinalização das MAP Quinases/fisiologia , Modelos Biológicos , Algoritmos , Animais , Canais de Cálcio/fisiologia , Sinalização do Cálcio/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Receptores de Inositol 1,4,5-Trifosfato , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Receptores Citoplasmáticos e Nucleares/fisiologia , Receptores de Fatores de Crescimento de Fibroblastos/fisiologia , Transdução de Sinais/fisiologia , Proteínas com Domínio T/genética , Proteínas de Xenopus/genética , Xenopus laevis , Quinases raf/fisiologiaRESUMO
The pancreatic acinar unit is a classical example of a polarized tissue. Even in isolation, these cells retain their polarity, and this has made them particularly useful for Ca2+ signaling studies. In 1990, we discovered that this cell has the capability of producing both local cytosolic and global Ca2+ signals. The mechanisms underlying this signal generation have now been established. Furthermore, it has become clear that the local signals are sufficient for the control of both fluid and enzyme secretion, whereas prolonged global signals are dangerous and give rise to acute pancreatitis, a disease where the pancreas digests itself.
Assuntos
Sinalização do Cálcio/fisiologia , Citosol/fisiologia , Retículo Endoplasmático/fisiologia , Inositol 1,4,5-Trifosfato/fisiologia , Pâncreas Exócrino/citologia , Cálcio/metabolismo , Comunicação Celular/fisiologia , Compartimento Celular/fisiologia , Membrana Celular/fisiologia , Polaridade Celular/fisiologia , Humanos , Potenciais da Membrana/fisiologia , Pâncreas Exócrino/fisiopatologia , Pancreatite/fisiopatologiaRESUMO
In neurons, depolarizing stimuli open voltage-gated Ca2+ channels, leading to Ca2+ entry and a rise in the cytoplasmic free Ca2+ concentration ([Ca2+]i). While such [Ca2+]i elevations are initiated by Ca2+ entry, they are also influenced by Ca2+ transporting organelles such as mitochondria and the endoplasmic reticulum (ER). This review summarizes contributions from the ER to depolarization-evoked [Ca2+]i responses in sympathetic neurons. As in other neurons, ER Ca2+ uptake depends on SERCAs, while passive Ca2+ release depends on ryanodine receptors (RyRs). RyRs are Ca2+ permeable channels that open in response to increases in [Ca2+]i, thereby permitting [Ca2+]i elevations to trigger Ca2+ release through Ca(2+)-induced Ca2+ release (CICR). However, whether this leads to net Ca2+ release from the ER critically depends upon the relative rates of Ca2+ uptake and release. We found that when RyRs are sensitized with caffeine, small evoked [Ca2+]i elevations do trigger net Ca2+ release, but in the absence of caffeine, net Ca2+ uptake occurs, indicating that Ca2+ uptake is stronger than Ca2+ release under these conditions. Nevertheless, by increasing ER Ca2+ permeability, RyRs reduce the strength of Ca2+ buffering by the ER in a [Ca2+](I)-dependent manner, providing a novel mechanism for [Ca2+]i response acceleration. Analysis of the underlying Ca2+ fluxes provides an explanation of this and two other modes of CICR that are revealed as [Ca2+]i elevations become progressively larger.
Assuntos
Canais de Cálcio/fisiologia , Sinalização do Cálcio/fisiologia , Retículo Endoplasmático/fisiologia , Neurônios/fisiologia , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologia , Animais , Cálcio/metabolismo , Canais de Cálcio/metabolismo , Citosol/metabolismo , Citosol/fisiologia , Eletrofisiologia , Retículo Endoplasmático/metabolismo , Inositol 1,4,5-Trifosfato/fisiologia , Potenciais da Membrana/fisiologia , Neurônios/metabolismo , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismoRESUMO
Lemon seedlings inoculated with Alternaria alternata develop a hypersensitive response (HR) that includes the induction of Phenylalanine ammonia-lyase (PAL, E. C. 4.3.1.5) and the synthesis of scoparone. The signal transduction pathway involved in the development of this response is unknown. We used several inhibitors of the Phosphoinositide (PI) animal system to study a possible role of Inositol-1,4,5-triphosphate (IP3) in the transduction of the fungal conidia signal in Citrus limon. The HR was only partially inhibited by EGTA, suggesting that not only external but internal calcium as well are necessary for a complete development of the HR. In this plant system, Alternaria alternata induced an early accumulation of the second messenger IP3. When lemon seedlings were watered long term with LiCl, an inhibitor of the phosphoinositide cycle, the IP3 production was reduced, and the LiCl-watered plants could neither induce PAL nor synthesize scoparone in response to fungal conidia. Furthermore, neomycin, a Phospholipase C (PLC, E. C. 3.1.4.3) inhibitor, also inhibited PAL induction and scoparone synthesis in response to A. alternata. These results suggest that IP3 could be involved in the signal transduction pathway for the development of the HR of Citrus limon against A. alternata.
Assuntos
Alternaria/patogenicidade , Citrus/fisiologia , Fosfatidilinositóis/metabolismo , Transdução de Sinais , Cafeína/farmacologia , Cálcio/farmacologia , Citrus/microbiologia , Cumarínicos/antagonistas & inibidores , Cumarínicos/metabolismo , Fibrinolíticos/farmacologia , Heparina/farmacologia , Inositol 1,4,5-Trifosfato/fisiologia , Neomicina/farmacologia , Fenilalanina Amônia-Liase/metabolismo , Fosfatidilinositóis/antagonistas & inibidores , Inibidores de Fosfodiesterase/farmacologia , Inibidores da Síntese de Proteínas/farmacologia , SementesRESUMO
Lemon seedlings inoculated with Alternaria alternata develop a hypersensitive response (HR) that includes the induction of Phenylalanine ammonia-lyase (PAL, E. C. 4.3.1.5) and the synthesis of scoparone. The signal transduction pathway involved in the development of this response is unknown. We used several inhibitors of the Phosphoinositide (PI) animal system to study a possible role of Inositol-1,4,5-triphosphate (IP3) in the transduction of the fungal conidia signal in Citrus limon. The HR was only partially inhibited by EGTA, suggesting that not only external but internal calcium as well are necessary for a complete development of the HR. In this plant system, Alternaria alternata induced an early accumulation of the second messenger IP3. When lemon seedlings were watered long term with LiCl, an inhibitor of the phosphoinositide cycle, the IP3 production was reduced, and the LiCl-watered plants could neither induce PAL nor synthesize scoparone in response to fungal conidia. Furthermore, neomycin, a Phospholipase C (PLC, E. C. 3.1.4.3) inhibitor, also inhibited PAL induction and scoparone synthesis in response to A. alternata. These results suggest that IP3 could be involved in the signal transduction pathway for the development of the HR of Citrus limon against A. alternata.
Assuntos
Alternaria/patogenicidade , Citrus/fisiologia , Citrus/virologia , Fosfatidilinositóis/metabolismo , Transdução de Sinais , Cafeína/farmacologia , Cálcio/farmacologia , Cumarínicos/antagonistas & inibidores , Cumarínicos/metabolismo , Fibrinolíticos/farmacologia , Heparina/farmacologia , Inositol 1,4,5-Trifosfato/fisiologia , Neomicina/farmacologia , Fenilalanina Amônia-Liase/metabolismo , Fosfatidilinositóis/antagonistas & inibidores , Inibidores de Fosfodiesterase/farmacologia , Inibidores da Síntese de Proteínas/farmacologia , SementesRESUMO
La hipertermia maligna es un síndrome farmocogenético asociado con la alteración de la regulación del calcio mioplásmico. Una modificación en el metabolismo del inositol 1,4,5 trifosfato (InsP3), hasido asociada con la fisiopatología de la hipertermia maligna. El objetivo del trabajo fue estudiar el efecto del InsP3 sobre la concentración intracelular de calcio ([CA²+]i) en fibras musculares obtenidas de sujetos no susceptibles y susceptibles a hipertermia maligna. La [CA²]i fue cuantificada mediante el uso de microelectrodos sensibles a CA²+. En susceptibles a hipertermia maligna la [CA²+]i fue más elevada que en las fibras musculares no suceptibles hipertemia maligna. La microinyección de InsP3 0,5 y 1 µM indujo una elevación significativa de la [CA²+]i, en ambos grupos musculares. Sin embargo, este incremento fue mayor en las fibras susceptibles a hipertermia maligna que en las no susceptibles a hipertermia maligna. La incubación de los músculos en soluciones con bajo contenido en Ca²+ o en nifedipina (10 µM) no modificó la elevación de [Ca²+]i mediana por el InsP3. El tratamiento con dantrolene (50 µM) redujo la [Ca²+]i, y bloqueó la elevación de la [Ca²+]i, inducida por el InsP3 en ambos grupos. Estos resultados sugieren (i) el posible papel del InsP3 como mediador químico en la liberación de Ca²+ desde los depósitos intracelulares; (ii) que el InsP3 podrá jugar un papel importante en la fisiopatología de la hipertermia maligna y (iii) que el efecto profiláctico y terapeútico del dantrolene podría estar relacionado con su efecto inhibitorio sobre la liberación de calcio intracelular mediada por el InsP3
Assuntos
Humanos , Feminino , Masculino , Inositol 1,4,5-Trifosfato/fisiologia , Cálcio , Hipertermia Maligna/diagnóstico , Hipertermia Maligna/metabolismo , Hipertermia Maligna/patologiaRESUMO
Invertebrate visual transduction involves a second messenger cascade process that leads to an increase in membrane conductance. The identity of the second messenger that gates the light-dependent channels is presently a major focus of attention. Cyclic GMP, inositol trisphosphate and Ca2+ are the most likely candidates for being such a messenger in the species studied so far. Here we review the available evidence for each of these molecules.
Assuntos
Células Fotorreceptoras de Invertebrados/fisiologia , Sistemas do Segundo Mensageiro/fisiologia , Visão Ocular/fisiologia , Animais , Canais de Cálcio/fisiologia , GMP Cíclico/fisiologia , Inositol 1,4,5-Trifosfato/fisiologiaRESUMO
Odorant detection takes place at the receptor neurons of the olfactory epithelium and odorant discrimination relies in an important degree on these chemosensory cells. Here we review the evidence for the participation of multiple transduction pathways in the mechanisms of odor recognition in olfactory neurons.
Assuntos
Odorantes , Nervo Olfatório/fisiologia , Neurônios Receptores Olfatórios/fisiologia , Olfato/fisiologia , Vertebrados/fisiologia , Animais , Monóxido de Carbono , AMP Cíclico/fisiologia , Humanos , Inositol 1,4,5-Trifosfato/fisiologia , Óxido Nítrico/fisiologia , Receptores Odorantes/fisiologia , Sistemas do Segundo Mensageiro/fisiologiaRESUMO
Invertebrate visual transduction involves a second messenger cascade process that leads to an increase in membrane conductance. The identity of the second messenger that gates the light-dependent channels is presently a major focus of attention. Cyclic GMP, inositol trisphosphate and Ca2+ are the most likely candidates for being such a messenger in the species studied so far. Here we review the available evidence for each of these molecules
Assuntos
Animais , Transdução de Sinal Luminoso/fisiologia , Células Fotorreceptoras de Invertebrados/fisiologia , Sistemas do Segundo Mensageiro/fisiologia , Canais de Cálcio/fisiologia , GMP Cíclico/fisiologia , Inositol 1,4,5-Trifosfato/fisiologiaRESUMO
Odorant detection takes place at the receptor neurons of the olfactory epithelium and odorant discrimination relies in an important degree on these chemosensory cells. Here we review the evidence for the participation of multiple transduction pathways in the mechanisms of odor recognition in olfactory neurons