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Regulation by glucose of oscillatory electrical activity and 5-HT/insulin relea...
Rosário, Luís M.; Barbosa, Rui M.; Antunes, Célia M.; Baldeiras, Inês E.; Silva, Amélia M.; Tomé, Ângelo R.; Santos, Rosa M.The glucose sensitivity of bursting electrical activity and pulsatile insulin release from pancreatic islets was determined in absence of functional KATP channels. Membrane potential, [Ca2+]i and 5-HT/insulin release were measured by intracellular recording, fura-2 fluorescence and 5-HT amperometry, respectively. Single mouse islets, bathed in tolbutamide or glibenclamide and high extracellular Ca2+ (Ca2+o), di...
Regulation by glucose of oscillatory electrical activity and 5-HT/insulin relea...
Antunes, Célia M.; Rosário, Luís M.; Barbosa, Rui M.; Silva, Amélia S.; Baldeiras, Inês E.; Tomé, Ângelo R.; Santos, Rosa M.The glucose sensitivity of bursting electrical activity and pulsatile insulin release from pancreatic islets was determined in absence of functional KATP channels. Membrane potential, [Ca2+]i and 5- HT/insulin release were measured by intracellular recording, fura-2 fluorescence and 5-HT amperometry, respectively. Single mouse islets, bathed in tolbutamide or glibenclamide and high extracellular Ca2+ (Ca2+o), d...
Selective stimulation of catecholamine release from bovine adrenal chromaffin c...
Tomé, Ângelo R.; Castro, Enrique; Santos, Rosa M.; Rosário, Luís M.Background 2-Methylthioadenosine 5'-triphosphate (2-MeSATP), formerly regarded as a specific P2Y (metabotropic) purinergic receptor agonist, stimulates Ca2+ influx and evokes catecholamine release from adrenal chromaffin cells. These cells express P2Y and P2X (ionotropic) purinoceptors, with the latter providing an important Ca2+ influx pathway. Using single cell calcium imaging techniques, we have determined ...
Functional distribution of Ca2+-coupled P2 purinergic receptors among adrenergi...
Tomé, Ângelo R.; Castro, Enrique; Santos, Rosa M.; Rosário, Luís M.Background Adrenal chromaffin cells mediate acute responses to stress through the release of epinephrine. Chromaffin cell function is regulated by several receptors, present both in adrenergic (AD) and noradrenergic (NA) cells. Extracellular ATP exerts excitatory and inhibitory actions on chromaffin cells via ionotropic (P2X) and metabotropic (P2Y) receptors. We have taken advantage of the actions of the purin...
Protein kinase C isoform specificity of cholinergic potentiation of glucose-ind...
Baldeiras, Inês E.; Santos, Rosa M.; Rosário, Luís M.Thymeleatoxin (TMX), an activator of Ca2+-sensitive protein kinase C (cPKC) isoforms, was used to assess the PKC isoform specificity of cholinergic potentiation of glucose (11 mM)-induced pulsatile 5-HT/insulin release (PIR) from single mouse pancreatic islets. TMX (100 nM) and carbachol (Cch, 50 \u03bcM) enhanced PIR ~ 3-fold while reducing the underlying [Ca2+]i oscillations (duration and amplitude) by ~ 40-5...
Alterações Da Morfologia Do Ilhéu De Langerhans Na Evolução Da Síndrome Diabéti...
Seiça, Raquel M.; Martins, M. João; Pessa, Pedro B.; Santos, Rosa M.; Rosário, Luís M. do; Suzuki, K. I.; Martins, Maria I.A deficiência da secreção de insulina na diabetes tipo 2 deve-se à menor massa de células ß e à disfunção destas células. A redução da massa celular na doença humana é variável, mas não superior a 50%. Não há alterações específicas da morfologia do ilhéu diabético humano; pode surgir deposição amilóide e, ocasionalmente, fibrose insular. Com este estudo cronológico comparativo entre ratos Wistar normais (W) e r...
Deficiência Primária Da Secreção De Insulina De Ilhéus Isolados De Ratos Goto-K...
Seiça, Raquel M.; Suzuki, K. I.; Santos, Rosa M.; Rosário, Luís M. doA deficiente secreção de insulina é factor determinante da diabetes tipo 2. Para avaliar a evolução da resposta secretora, foi feito um estudo cronológico comparativo entre ratos Wistar normais (W) e ratos Goto-Kakizaki (GK), um modelo genético de diabetes tipo 2 não obesa, da dinâmica da secreção de insulina de ilhéus de Langerhans isolados em resposta à glicose e à arginina, por técnicas de isolamento e de pe...
Morphological changes of islet of Langerhans in an animal model of type 2 diabe...
Seiça, Raquel M; Martins, M João; Pessa, Pedro B; Santos, Rosa M; Rosário, Luís M do; Suzuki, K I; Martins, Maria IThe impairment of insulin secretion, a major feature of type 2 diabetes, is caused by beta-cell mass reduction and functional failure. Pancreatic beta-cell mass reduction is variable in humans, not exceeding 50%, and has been associated with amyloid deposits. In the present study, we have chronologically compared the endocrine pancreas morphology of Wistar control rats (W) and Goto-Kakizaki (GK) rats, an animal...
Naloxone inhibits nicotine-induced receptor current and catecholamine secretion...
Tomé, Angelo R.; Izaguirre, Victor; Rosário, Luís M.; Ceña, Valentín; González-García, CarmenNicotine-induced catecholamine (CA) secretion and inward ionic currents were inhibited by the opioid antagonist naloxone in cultured bovine chromaffin cells. Naloxone inhibited nicotine-induced CA secretion, as detected by an on-line real-time electrochemical technique, in a dose-dependent manner (IC50=29 [mu]M). In voltage-clamped chromaffin cells, nicotine (10 [mu]M) evoked an average peak inward current of -...
Isoform-specific inhibition of voltage-sensitive Ca2+ channels by protein kinas...
Sena, Cristina M.; Santos, Rosa M.; Standen, Nick B.; Boarder, Michael R.; Rosário, Luís M.Selective protein kinase C (PKC) activators and inhibitors were used to investigate the involvement of specific PKC isoforms in the modulation of voltage-sensitive Ca2+ channels (VSCCs) in bovine adrenal chromaffin cells. Exposure to the phorbol ester phorbol-12,13-dibutyrate (PDBu) inhibited the Ca2+ currents elicited by depolarizing voltage steps. This inhibition was occluded by the PKC-specific inhibitor Ro ...
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