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Developmental changes in glutamine transport by rat jejunal basolateral membrane vesicles
F T al-Mahroos1, N Abumrad, F K Ghishan
1Department of Pediatrics, Molecular Physiology, Biophysics and Surgery, Vanderbilt University, Nashville, Tennessee 37232.
Summary
Glutamine uptake in rat jejunum shows significant developmental changes, with higher transporter activity in suckling and weanling rats compared to adults. This reflects increased transporter expression during rapid growth phases.
Area of Science:
- Physiology
- Developmental Biology
- Gastroenterology
Background:
- Glutamine is a crucial amino acid for rapidly proliferating cells.
- Understanding glutamine transport ontogeny is vital for comprehending nutrient absorption during development.
Purpose of the Study:
- To investigate the developmental changes in glutamine uptake by jejunal basolateral membrane vesicles (BLMV).
- To characterize the kinetic properties and identify the transporters involved in jejunal glutamine transport during different life stages.
Main Methods:
- Uptake studies using isolated jejunal basolateral membrane vesicles (BLMV) from suckling, weanling, and adult rats.
- Kinetic analysis (Vmax, Km) and inhibition studies to identify transporter systems.
- Assessment of Na+ gradient dependence and temperature/pH optima.
Main Results:
- Glutamine uptake is a carrier-mediated, Na+-dependent process with optimal pH 7.0.
- Two main transport systems were identified: a Na+-dependent System A and a Na+-independent System L.
- Vmax for both Na+-dependent and Na+-independent systems was significantly higher in suckling and weanling rats compared to adults.
- Higher overshoot phenomenon observed in suckling rats indicates greater transporter activity.
Conclusions:
- Jejunal glutamine uptake exhibits significant ontogeny, with increased transporter activity and/or number during suckling and weaning periods.
- These developmental changes in glutamine transport are likely adaptations to support rapid cellular proliferation and differentiation in the immature intestine.