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L‐[ 3 H]Adenosine, a New Metabolically Stable Enantiomeric Probe for Adenosine Transport Systems in Rat Brain Synaptoneurosomes
Author(s) -
Gu J. G.,
Delaney S.,
Sawka A. N.,
Geiger J. D.
Publication year - 1991
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.1471-4159.1991.tb08184.x
Subject(s) - adenosine , adenosine kinase , adenosine deaminase , chemistry , adenosine a1 receptor , adenosine receptor , biochemistry , agonist , receptor
The stereoenantiomers D‐[ 3 H]adenosine and L‐[ 3 H]adenosine were used to study adenosine accumulation in rat cerebral cortical synaptoneurosomes. L‐Adenosine very weakly inhibited rat brain adenosine deaminase (ADA) activity with a K i value of 385 μ M . It did not inhibit rat brain adenosine kinase (AK) activity, nor was it utilized as a substrate for either ADA or AK. The rate constants (fmol/mg of protein/s) for L‐[ 3 H]adenosine accumulation measured in assays where transport was stopped either with inhibitor‐stop centrifugation or with rapid filtration methods were 82 ± 14 and 75 ± 10, respectively. Using the filtration method, the rates of L‐[ 3 H]adenosine accumulation were not significantly different from the value of 105 ± 15 fmol/mg of protein/s measured for D‐[ 3 H]adenosine transport. Unlabeled D‐adenosine and nitrobenzylthioinosine, both at a concentration of 100 μ M , reduced the levels and rates of L‐[ 3 H]adenosine accumulation by >44%. These findings suggest that L‐adenosine, a metabolically stable enantiomeric analog, and the naturally occurring D‐adenosine are both taken up by rat brain synaptoneurosomes by similar processes, and as such L‐adenosine may represent an important new probe with which adenosine uptake may be studied.