Sodium-dependent uptake of nucleosides by dissociated brain cells from the rat.
Sodium-dependent 3H-labeled nucleoside transport was studied using a mixed population of dissociated brain cells from adult rats. The accumulation of [3H]adenosine during brief (15-s) incubation periods was significantly greater in the presence of 110 mM Na+ than in its absence. This occurred at substrate concentrations that ranged from 0.25 to 100 microM. Similar findings were observed for the rapid accumulation of [3H]uridine. Kinetically, the rapid accumulation of [3H]adenosine in both the absence and the presence of Na+ was best described by a two-component system. In the presence of Na+, the KT and Vmax values for the high-affinity affinity component were 0.9 microM and 8.9 pmol/mg of protein/15 s, and those for the low-affinity component were 313 microM and 3,428 pmol/mg of protein/15 s, respectively. In the absence of Na+, the KT value for the high-affinity component was significantly higher (1.8 microM). [3H]Uridine accumulation was best described kinetically by a one-component system that in the presence of Na+ had KT and Vmax values of 1.0 mM and 2.6 nmol/mg of protein/15 s, respectively. As was found for [3H]adenosine, in the absence of Na+, the KT value was significantly higher (1.8 mM). The sodium-dependent transport of [3H]adenosine was inhibitable by ouabain and 2,4-dinitrophenol. Of the three nucleoside transport inhibitors tested, only nitrobenzylthioninosine 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.
Johnston
M E
ME
School of Dentistry, University of Manitoba, Winnipeg, Canada.
Geiger
J D
JD
D000241:Adenosine / Q000493:pharmacokinetics; D000818:Animals; D001921:Brain / Q000378:metabolism*; D004109:Dilazep / Q000494:pharmacology; D004176:Dipyridamole / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009705:Nucleosides / Q000493:pharmacokinetics*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D013868:Thioinosine / Q000031:analogs & derivatives / Q000494:pharmacology; D014529:Uridine / Q000493:pharmacokinetics
D009705:Nucleosides; D013868:Thioinosine; D010042:Ouabain; D004176:Dipyridamole; D012964:Sodium; D004109:Dilazep; C001789:4-nitrobenzylthioinosine; D000241:Adenosine; D014529:Uridine