title: L-[3H]adenosine, a new metabolically stable enantiomeric probe for adenosine transport systems in rat brain synaptoneurosomes.
abstract: The stereoenantimers D-[3H]adenosine and L-[3H]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 Ki value of 385 microM. 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-[3H]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-[3H]adenosine accumulation were not significantly different from the value of 105 +/- 15 fmol/mg of protein/s measured for D-[3H]adenosine transport. Unlabeled D-adenosine and nitrobenzylthiolnosine, both at a concentration of 100 microM, reduced the levels and rates of L-[3H]adenosine accumulation by greater than 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.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Manitoba Faculty of Medicine, Winnipeg, Canada.
authors.forename: J G
authors.initials: JG
authors.lastname: Gu
authors.forename: S
authors.initials: S
authors.lastname: Delaney
authors.forename: A N
authors.initials: AN
authors.lastname: Sawka
authors.forename: J D
authors.initials: JD
authors.lastname: Geiger
mesh_terms: D000241:Adenosine / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D015394:Molecular Structure; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism; D013574:Synaptosomes / Q000378:metabolism*; D013868:Thioinosine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D013868:Thioinosine; C001789:4-nitrobenzylthioinosine; D000241:Adenosine