Change in membrane elastic modulus on activation of glucose transport system of brush border membrane vesicles studied by osmotic swelling and dynamic light scattering.
The cell membrane having a transport system is inferred to be flexible when its function is being activated. For the brush border membrane vesicles prepared from rat small intestine, which have the co-transport system of Na+ and glucose, the membrane elasticity was measured as a function of the d-glucose concentration in the presence of Na+ ions. The elastic modulus of the vesicle membrane was obtained by an osmotic swelling method. Osmolality was changed by diluting the extravesicular d-mannitol concentration. The change in the diameter of the membrane vesicle in response to an osmolality change was measured by the dynamic light-scattering method. The elastic modulus of the vesicle membrane decreased from 150 dyn/cm to 80 (45) dyn/cm with the increase of d-glucose, from 0 mM to 10(30) mM in the presence of 10 mM Na+ ions. On the other hand, in the presence of 1 mM phlorizin, a glucose-transport inhibitor, the elastic modulus remained at a constant value of 160 dyn/cm in the same range of the d-glucose concentration. This indicates that the vesicle membrane becomes flexible when its transport function is activated. In a broad osmolality range, the brush border membrane vesicle showed cycles of "swell-burst-reseal". The vesicle membrane became flexible after every cycle, namely, the modulus was 150, 120, and 55 in units of dyn/cm in the presence of 1 mM d-glucose and 50 mM Na+ ions.
Miyamoto
S
S
Mitsubishi-Kasei Institute of Life Sciences, Tokyo, Japan.
Maeda
T
T
Fujime
S
S
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D004548:Elasticity; D007421:Intestine, Small / Q000502:physiology*; D007700:Kinetics; D008027:Light; D008565:Membrane Proteins / Q000032:analysis; D008871:Microvilli / Q000502:physiology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009995:Osmosis; D051381:Rats; D011919:Rats, Inbred Strains; D012542:Scattering, Radiation; D013393:Sucrase / Q000378:metabolism
D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D000469:Alkaline Phosphatase; D013393:Sucrase