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Fotocópia
Id: lil-362377
Autor: L. A, Saldena; A. J. C, Sasso; Cincunegui, Liliana M; Carra, Graciela E; Codina, Maria Victoria; Saravi, J. D.
Título: Pharmacological Suppression of rat distal colon chloride secretion requires two blockers
Fonte: Acta gastroenterol. latinoam;33(3):119-127, Aug. 2003. tab, graf.
Idioma: en.
Resumo: Rat distal colon epithelium is frequently employed to assess the effect of natural and synthetic chemicals on chloride secretion. Inhibition of chloride secretion is often reported as the loop diuretic-sensitive portion of short-circuit current (Isc). The present work challenges the hypothesis that a loop diuretic alone is able to fully abolish chloride secretion. Isolated mucosa preparations were mounted in an Ussing chamber. The effects on short-circuit current of replacement of normal Ringer by a low (2.5 mmol/L) Cl solution and of blockers of basolateral Na, K, 2 Cl symport (bumetanide), apical Cl channels (diphenylamine-2-carboxylate, DPC), and anion exchange (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid, SITS) alone and combined were assessed. Low Cl reversibly decreased Isc by 76%. In normal Ringer, bumetanide decreased Isc by 65%. SITS also had a significant effect at the serosal side, but not at the apical side, where DPC caused a 40% decrease. Chloride replacement, bumetanide and DPC, but not SITS, increased epithelial resistivity. Combined blockade of Na, K, 2 Cl symport and apical Cl channels, of Na, K, 2 Cl symport and anion antiport, or of anion antiport and apical Cl channels was needed to achieve reduction of short circuit current to the same extent seen with chloride replacement. Present results indicate that Isc of the unstimulated epithelium is mostly due to chloride secretion, and at least two blockers are required to abolish it. This fact should be taken into account in studies of chloride secretion-stimulating agents.
Descritores: Ácido 4-Acetamido-4'-isotiocianatostilbeno-2,2'-dissulfônico
Bumetanida
Bloqueadores dos Canais de Cálcio
Cloretos
Colo
Difenilamina
Diuréticos
-Colo
Relação Dose-Resposta a Droga
Combinação de Medicamentos
Condutividade Elétrica
Mucosa Intestinal
Ratos Wistar
Limites: Animais
Masculino
Ratos
Responsável: BR1.1 - BIREME


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Fotocópia
Id: lil-79122
Autor: Romero, Pedro J; Finol, Héctor J.
Título: Tannic acid as a marker for membrane sidedness of human red cell vesicles
Fonte: Acta cient. venez;40(2):107-12, 1989. ilus.
Idioma: en.
Projeto: Consejo de Desarrollo Cientifico y Humanistico. Universidad Central de Venezuela.
Resumo: Membrane sidedness of human eythrocytes was investigated in inside-out vesicles (IOV's), ghosts and intact cells by means of transmission electron microscopy (e.m.) after tannic acid fixation. No gross difference in appeearance of either membrane surface was observed when IOV's were subjected to conventional e.m. preparation. This included in addition to tannic acid, a double fixation with glutaraldehyde and osmium, followed by "en bloc" and thin section staining with uranyl acetate and lead citrate. By contrast, if IOV's were treated with a high EDTA concentration (2-5 mM) before tannic fixation, granular, electron-dense deposits were found on one of the surfaces. The presence of such a meterial was unaffected by neuraminidase treatment prior to the EDTA step. On the hand, red cells show no electron-dense deposits when exposed to EDTA (5 mM) unless they presented a light cytoplasm and an altered membrane appearance. Such a material was only observed on the inner membrane surface. Furthermore, a similar distribution of such deposits following EDTA treatment was also found in white ghosts before being induced to vesiculate. These results indicate that tannic acid can be employed as a marker for the cytoplasmic surface of the human erythrocyte membrane when used in combination with EDTA
Descritores: Ácido 4-Acetamido-4'-isotiocianatostilbeno-2,2'-dissulfônico/farmacologia
ATPases Transportadoras de Cálcio/antagonistas & inibidores
Membrana Eritrocítica/enzimologia
-Ácido 4-Acetamido-4'-isotiocianatostilbeno-2,2'-dissulfônico/análogos & derivados
ATPase de Ca(2+) e Mg(2+)/sangue
ATPase Trocadora de Sódio-Potássio/sangue
Responsável: VE1.1 - Biblioteca Humberto Garcia Arocha



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