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J Physiol Vol 228, Issue 1 pp 105-113
Copyright © 1973 by The Physiological Society
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The rate equation and activation energies for the uptake of {alpha}-aminoisobutyric acid by mouse brain slices

 Stephen R. Cohen

1. The initial influx of the amino acid analogue AIB at medium concentrations of 0·05-20 mM into mouse cerebrum slices incubated at temperatures from 20 to 45° C follows the rate law v = Vmax/(1 + Kt/S)+kuS. The linear term kuS arises from an unsaturable process of concentrative uptake.

2. At 37° C the kinetic constants are Kt = 1·12 mM; Vmax = 0·39 µmole AIB/g final wet wt. of slices. min; and ku = 0·054 µmole AIB/g final wet wt. of slices. mM-AIB. min.

3. At infinitesmal substrate concentrations 13% of influx is via the unsaturable process. This rises to 73% for 20 mM substrate.

4. Kt is independent of temperature. The other constants increase rapidly with temperature. Arrhenius activation energies are 14·1 kcal/mole for Vmax and 17·4 kcal/mole for ku.






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