Effects of membrane potential on Na cotransports in eel intestinal brush-border membrane vesicles: Studies with a fluorescent dye |
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Authors: | Giuseppe Cassano Michele Maffia Sebastiano Vilella Carlo Storelli |
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Affiliation: | (1) Laboratorio di Fisiologia, Dipartimento di Biologia, Università de Lecce, 73100 Lecce, Italy |
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Abstract: | Summary The Na-dependent transport of a number of organic molecules (d-glucose,l-proline,l-alanine,l-phenylalanine) in brush-border membrane vesicles isolated from the intestine of the eel (Anguilla anguilla) was monitored by recording the fluorescence quenching of the voltage-sensitive cyanine dye 3,3-diethylthiacarbocyanine iodide (DiS-C2(5)). The experimental approach consisted of: a) generating an inside-negative membrane potential mimicking in vivo conditions: b) measuring the rate of membrane potential decay (i.e., the rate of fluorescence quenching decay) due to Na-neutral substrate cotransport. Rates of membrane potential decay showed saturation on substrate concentration andKapp values (the substrate concentration giving 50% of the maximal rate) were estimated for Na-dependent transport ofd-glucose (0,099mm),l-alanine (0.516mm),l-proline (0.118mm) andl-phenylalanine (2.04mm). The influence of an inside-negative membrane potential on the affinity of the transporter for glucose and for sodium is discussed. |
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Keywords: | Na cotransport eel intestine brush-border membrane vesicles cyanine dye membrane potential |
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