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D-glucose uptake is increased in jejunal brush-border membrane vesicles from hyperthyroid chicks
H Debiec1, H S Cross, M Peterlik
1Department of Biochemistry and Experimental Medicine, Child's Health Center, Warsaw, Poland.
Acta Endocrinologica
|April 1, 1989
Summary
Thyroid hormone (T3) significantly enhances D-glucose uptake in chick jejunal vesicles by increasing carrier activity, not by altering electrochemical gradients. This suggests improved intestinal glucose absorption during hyperthyroidism.
Area of Science:
- Endocrinology
- Gastroenterology
- Molecular Biology
Background:
- Thyroid hormones play a crucial role in regulating intestinal function and nutrient absorption.
- The specific mechanisms by which thyroid hormones influence glucose transport in the small intestine remain incompletely understood.
Purpose of the Study:
- To investigate the effect of thyroid hormone (T3) on Na+-dependent D-glucose uptake in chick jejunal brush-border membrane vesicles.
- To elucidate the underlying mechanisms of T3-mediated alterations in glucose transport.
Main Methods:
- Isolation of jejunal brush-border membrane vesicles from chicks with altered thyroid status (T3-treated or propylthiouracil-treated and repleted).
- Measurement of D-glucose uptake under various Na+ gradient and transmembrane potential conditions.
- Kinetic analysis of D-glucose transport using tracer exchange and voltage-clamp experiments.
Main Results:
- T3 markedly stimulated Na+-dependent D-glucose uptake.
- T3 did not affect Na+ permeability or transmembrane potential.
- T3 administration increased the maximal velocity (Vmax) of D-glucose transport without altering the Michaelis constant (Km).
Conclusions:
- T3 increases the activity of Na+-dependent D-glucose carriers in the jejunal brush-border membrane.
- This enhanced carrier activity contributes to a greater rate of intestinal glucose absorption in hyperthyroid states.