Independent modulation by food supply of two distinct sodium-activated D-glucose transport systems in the guinea pig jejunal brush-border membrane.
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.
Brot-Laroche
E
E
Centre de Recherches sur la Nutrition, Meudon, France.
Dao
M T
MT
Alcalde
A I
AI
Delhomme
B
B
Triadou
N
N
Alvarado
F
F
D000818:Animals; D004032:Diet; D004435:Eating; D005260:Female; D005947:Glucose / Q000378:metabolism; D006168:Guinea Pigs; D007583:Jejunum / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*; D013217:Starvation
D009004:Monosaccharide Transport Proteins; D012964:Sodium; D005947:Glucose