myo-inositol transport in rat intestinal brush border membrane vesicles, and its inhibition by D-glucose.
The uptake of myo-inositol into rat intestinal brush border membrane vesicles (BBMV) has been investigated. It is demonstrated that myo-inositol is transported into the vesicles by a secondary active process, specifically using the sodium gradient as the driving force. In the absence of sodium gradient, the transport reaction is still sodium dependent, and rheogenic, indicating that a myo-inositol/sodium cotransport is likely to occur. A kinetic analysis shows an hyperbolic saturation process with a Km of 0.16 +/- 0.02 mM with respect to myo-inositol and Vmax of 68.5 +/- 21.2 pmol/min per mg protein. The transport is inhibited by D-glucose, phloridzin and few other sugars. The mechanism of D-glucose inhibition appears to be of the mixed type. Finally, the myo-inositol transport is trans-activated by myo-inositol itself, but not by D-glucose. It is concluded that myo-inositol is transported into rat intestine BBMV by a specific transport system, which is also able to bind D-glucose, but not efficiently transport it across the membrane.
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Istituto di Fisiologia Generale, Università di Bari, Italy.
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Prezioso
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D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D004594:Electrophysiology; D005947:Glucose / Q000493:pharmacokinetics*; D005960:Glucosides / Q000493:pharmacokinetics; D066298:In Vitro Techniques; D007294:Inositol / Q000493:pharmacokinetics*; D007408:Intestinal Absorption / Q000502:physiology*; D008871:Microvilli / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000502:physiology
D005960:Glucosides; D009004:Monosaccharide Transport Proteins; D007294:Inositol; D012964:Sodium; D005947:Glucose