Independent modulation by food supply of two distinct sodium-activated D-glucose transport systems in the guinea pig jejunal brush-border membrane.
AUTOR(ES)
Brot-Laroche, E
RESUMO
D-glucose transport across the intestinal brush-border membrane involves two transport systems designated here as systems 1 and 2. Kinetic properties for both D-glucose and methyl alpha-D-glucopyranoside transport were measured at 35 degrees C by using brush-border membrane vesicles prepared from either control, fasted (48 hr), or semistarved (10 days) animals. The results show the following: (i) The sugar influx rate by simple diffusion was identical under either altered condition. (ii) Semistarvation stimulated D-glucose uptake by system 2 (both its Vmax and Km increased), whereas system 1 was untouched. (iii) Fasting increased the capacity of system 1 without affecting either Km of system 1 or Vmax and Km of system 2. The effect of fasting on Vmax of system 1 cannot be attributed to indirect effects from changes in ionic permeability because the kinetic difference between control and fasted animals persisted when the membrane potential was short-circuited with equilibrated K+ and valinomycin. This work provides further evidence for the existence of two distinct sodium-activated D-glucose transport systems in the intestinal brush-border membrane, which adapt independently to either semistarvation or fasting.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=281973Documentos Relacionados
- Chloride ion transport into pig jejunal brush-border membrane vesicles.
- Mechanisms of zinc transport into pig small intestine brush-border membrane vesicles.
- Jejunal brush-border folate hydrolase. A novel enzyme.
- Demonstration of Electrogenic Na+-dependent D-glucose Transport in Intestinal Brush Border Membranes
- Kinetics of sodium-dependent solute transport by rabbit renal and jejunal brush-border vesicles using a fluorescent dye.