Adenosine transport systems on dissociated brain cells from mouse, guinea-pig, and rat

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Abstract
The kinetics and sodium dependence of adenosine transport were determined using an inhibitorstop method on dissociated cell body preparations obtained from mouse guinea-pig and rat brain. Transport affinity (KT) values for the high affinity adenosine transport systems (KT(H)) were significantly different between these three species; mean ±SEM values were 0.34 ±0.1 in mouse, 0.9 ±0.2 in rat, and 1.5±0.5 μM in guinea-pig. The KT values for the low affinity transport system (KT(L)) were not different between the three species. Brain cells from rat displayed a significantly greater maximal capacity to accumulate [3H]adenosine (Vmax) than did mouse or guinea-pig for the high affinity system, or than did mouse for the low affinity system. When sodium chloride was replaced in the transport medium with choline chloride, the KT(H) values for guinea-pig and rat were both increased by approximately 100%; only in rat did the change reach statistical significance. The sodium-dependence of adenosine transport in mouse brain was clearly absent. The differences between KT(H) values in mouse and those in guinea-pig or rat were accentuated in the absence of sodium. The differences in kinetic values, ionic requirements, and pharmacological characteristics between adenosine transporters in CNS tissues of mouse guinea-pig and rat may help account for some of the variability noted among species in terms of their physiological responses to adenosine.