Triiodothyronine stimulates 2-deoxy-D-glucose uptake by organ cultured embryonic chick small intestine.
The possible contribution of increased D-glucose absorption from the intestine to the impairment of oral glucose tolerance in hyperthyroidism was evaluated by investigating the influence of T3 on different pathways of D-glucose transport, utilizing an organ culture system of embryonic chick small intestinal explants. T3, when present in the culture medium at a concentration between 10(-10)-10(-8) mol/l, had no effect on uptake of alpha-methyl-D-glucoside, but stimulated uptake of 2-deoxy-D-glucose by the intestinal epithelium in a dose-dependent fashion. T3 thereby enhanced the maximal velocity of a saturable, cytochalasin B-sensitive but phloretin-insensitive 2-deoxy-D-glucose transport system with an apparent Km of 7 mmol/l. The combined data are consistent with the assumption that T3 can enhance D-glucose entry into the intestinal epithelium through stimulation of a low-affinity transport system at the brush-border membrane of enterocytes. Our findings provide a basis for the explanation of adaptive modulation of intestinal glucose absorption in hyperthyroidism.
Prager
C
C
Department of General and Experimental Pathology, University of Vienna Medical School, Austria.
Cross
H S
HS
Peterlik
M
M
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002642:Chick Embryo; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects; D007421:Intestine, Small / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D009924:Organ Culture Techniques; D014284:Triiodothyronine / Q000494:pharmacology*
D003837:Deoxy Sugars; D014284:Triiodothyronine; D003847:Deoxyglucose