Stimulation of Na+‐Dependent, Veratridine‐Sensitive Synaptosomal Amino Acid Uptakes by Serum Albumin

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Abstract
Bovine serum albumin (BSA) is shown to stimulate selectively the synaptosomal uptakes of those amino acids that are dependent on external Na+ and that are inhibited by veratridine. Thus, the stimulation can be seen in the case of aspartic acid, glutamic acid, glycine, proline, and γ-aminobutyric acid, but not with serine and threonine. Further, studies on the interaction of veratridine, valinomycin, and BSA on the uptake of proline suggest that the primary action of the albumin is to increase the influx of proline. Such an action could result as a consequence of stabilization of the Na+ gradient by increased endogenous levels of ATP. Intrasynaptosomal ATP was increased in the presence of BSA but significantly decreased by veratridine.