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 and Kapp values (the substrate concentration giving 50% of the maximal rate) were estimated for Na-dependent transport of d-glucose (0,099 mm), l-alanine (0.516 mm), l-proline (0.118 mm) and l-phenylalanine (2.04 mm). The influence of an inside-negative membrane potential on the affinity of the transporter for glucose and for sodium is discussed.
Effects of membrane potential on Na cotransports in eel intestinal brush-border membrane vesicles: Studies with a fluorescent dye
CASSANO, Giuseppe;
1988-01-01
Abstract
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 and Kapp values (the substrate concentration giving 50% of the maximal rate) were estimated for Na-dependent transport of d-glucose (0,099 mm), l-alanine (0.516 mm), l-proline (0.118 mm) and l-phenylalanine (2.04 mm). The influence of an inside-negative membrane potential on the affinity of the transporter for glucose and for sodium is discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
