Alternate models for shared carriers or a single maturing carrier in hexose uptake into rabbit jejunum in vitro.
The uptake (tissue accumulation) of three hexoses into rabbit jejunum was measured in a flux chamber in conditions of effective stirring. Glucose uptake was inhibited by galactose or 3-O-methylglucose: 1-40 mM galactose caused a progressive decline in glucose uptake; 1-5 mM 3-O-methylglucose inhibited glucose uptake but higher concentrations of 3-O-methylglucose had no further effect. When 1-40 mM 3-O-methylglucose was added to glucose plus galactose there was a further decrease in the uptake of glucose; adding 1-40 mM galactose to glucose plus 3-O-methylglucose also produced a decrease in glucose uptake. Both glucose and 3-O-methylglucose inhibited uptake of galactose but the pattern of inhibition varied between the two sugars. The uptake of 3-O-methylglucose was also inhibited by glucose and by galactose, but the uptake of 3-O-methylglucose in the presence of either galactose or glucose was no further reduced by adding the third hexose. Graphical analysis and analysis by non-linear regression both showed that neither the single Michaelis-Menten function, nor the single Michaelis-Menten-plus-competitive-inhibition function was appropriate for any of these data. The results are consistent with the hypothesis that either there are multiple (at least three) intestinal carriers for hexoses; alternatively that there is a single carrier whose transport properties for the three hexoses change differentially during cell maturation and migration up the villus.
D019325:3-O-Methylglucose; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005260:Female; D005690:Galactose / Q000378:metabolism* / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D007583:Jejunum / Q000378:metabolism*; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism* / Q000494:pharmacology; D008759:Methylglycosides / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D011817:Rabbits
D008757:Methylglucosides; D008759:Methylglycosides; D009004:Monosaccharide Transport Proteins; D019325:3-O-Methylglucose; D005947:Glucose; D005690:Galactose