myo-Inositol binding and transport in brush border membranes of rat kidney.
Using hypotonically treated brush border membranes, binding and transport of myo-inositol were examined. By hypotonic treatment, both total and non-specific uptake decreased significantly, but specific uptake was not affected. myo-Inositol release from membranes preloaded by incubation for 2 min was very rapid and about 98% of preloaded myo-inositol was released in 5 min of incubation. However, myo-inositol release from membranes  preloaded by incubation for 20 min was fairly slow and 50% of myo-inositol remained in the membranes even after 10 min of incubation. Uptake of myo-inositol decreased by the increase of osmolarity in the medium. However, effect of osmolarity on the uptake was less significant when myo-inositol concentration was lower. Under conditions in which mainly binding occurred, myo-inositol binding to the membranes was measured. Two binding systems were demonstrated and high affinity site could bind 22 pmol/mg protein at most and the apparent Km value was 8.3 muM. Both binding and transport processes were dependent on Na+ and enhanced by Na+-gradient.
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D007294:Inositol / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D008353:Mannitol / Q000378:metabolism; D009994:Osmolar Concentration; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology
D008353:Mannitol; D007294:Inositol; D012964:Sodium; D011188:Potassium