Abstract
1. Rat brain slices strongly concentrate L-histidine from the suspending medium. D-Histidine is also concentrated well. However there is some degree of stereospecificity between L- and D-histidine. Urocanic acid is not concentrated.
2. Active histidine uptake is markedly suppressed by dinitrophenol and in glucose-free medium.
3. L- And D-methionine inhibit the up-take of L- and n-histidine but the uptake of DL-methionine is stimulated by L-histidine.
4. When brain slices prepacked with L-histidine are incubated with methionine, a very rapid release of L-histidine takes place. On the other hand, prepacking slices with L-histidine stimulates the uptake of DL-methionine.
5. Exchange diffusion between L-histi-dine in slices and DL-methionine in the me-dium occurs in a mole-to-mole ratio.
6. The efflux rate of DL-methionine is much greater than the two isomers of histi-dine.
7. The uptake of histidine by rat brain in vivo is stereoselective.
The author is greatly indebted to Prof. M. Suda for his encouragement and advice during the work and for help in preparing the manuscript.
