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Sodium‐Dependent Uptake of Nucleosides by Dissociated Brain Cells from the Rat
Author(s) -
Johnston Mark E.,
Geiger Jonathan D.
Publication year - 1989
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1989.tb10900.x
Subject(s) - adenosine , nucleoside , ouabain , sodium , chemistry , uridine , population , incubation , biochemistry , substrate (aquarium) , efflux , biophysics , stereochemistry , biology , rna , ecology , demography , organic chemistry , sociology , gene
Sodium‐dependent 3 H‐labeled nucleoside transport was studied using a mixed population of dissociated brain cells from adult rats. The accumulation of [ 3 H]adenosine during brief (15‐s) incubation periods was significantly greater in the presence of 110 μ M Na + than in its absence. This occurred at substrate concentrations that ranged from 0.25 to 100 μ M . Similar findings were observed for the rapid accumulation of [ 3 H]uridine. Kinetically, the rapid accumulation of [ 3 H]adenosine in both the absence and the presence of Na + was best described by a two‐component system. In the presence of Na + , the K T and V max values for the high‐affinity component were 0.9 μ M and 8.9 pmol/mg of protein/15 s, and those for the low‐affinity component were 313 μ M and 3,428 pmol/mg of protein/15 s, respectively. In the absence of Na + , the K T value for the high‐affinity component was significantly higher (1.8 μ M ). [ 3 H]Uridine accumulation was best described kinetically by a one‐component system that in the presence of Na + had K T and V max values of 1.0 m M and 2.6 nmol/mg of protein/15 s, respectively. As was found for [ 3 H]adenosine, in the absence of Na + , the K T value was significantly higher (1.8 m M ). The sodium‐dependent transport of [ 3 H]adenosine was inhibitable by ouabain and 2,4‐dinitrophenol. Of the three nucleoside transport inhibitors tested, only nitrobenzylthioinosine demonstrated high affinity and selectivity in blocking the sodium component. Thus, high‐affinity sodium‐dependent nucleoside transport systems, in addition to facilitated diffusion systems, exist on brain cells from adult rats.