Glutamate uptake, Assay

Fig. 2. Acidification of small synaptic vesicles by glutamate and chloride in synap-tosomes. The acidification assay was performed as described in section 3.2 of this chapter. Two representative experiments with intact (upper trace) or SLO-permeabilized (lower trace) synaptosomes are shown. The ordinate gives the changes of absorbance obtained (A 492-530). Final concentrations of potassium glutamate (Glut), KCl, and ammonium sulfate (NH/) were 10 mM, 45 mM and 30 mM, respectively. The uptake of glutamate and chloride result in an acidification of the lumen of small synaptic vesicles, which increases the vesicular uptake of acridine orange, resulting in a decrease in the amount of extravesicular dye. This acidification can be only observed when the plasma membrane is permeabilized...

Cell fractionation studies of homogenates of the gastric mucosa have demonstrated that the intrinsic factor is found both in mitochondria and the supernatant fluid. The factor remains difficult to assay a variety of methods have been used, but none is entirely satisfactory. These methods include (1) administration of intrinsic factor preparation to gastrectomized animals (rats or hogs) (2) measurement of vitamin 6 2 binding capacity of the preparation (3) measurement of vitamin Bi2 uptake in tissue and (4) evaluation of the inhibition of cobamide coenzyme activity in the glutamate isomerase reaction. 

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