A kinetic study of the in vitro uptake of [3H]dopamine over a wide range of concentrations by rat striatal preparations

The uptake of 3H]dopamine was investigated in a number of rat striatal preparations. Kinetic analysis of the rate of uptake by striatal slices indicated that at least two different saturable mechanisms for the catecholamine exist in this region, in addition to a first-order component. One of the uptake mechanisms has a high affinity for 3H]dopamine and the other a low affinity. Distinct high and low affinity systems were also observed for the uptake of 3H]dopamine by dispersed cell preparations of the rat striatum. Striatal synaptosomes appeared to have only a high affinity mechanism and a first-order component. The high affinity mechanisms are active transport mechanisms but the low affinity mechanisms are not unequivocably active transport systems. It is concluded that at least two sites for the uptake of 3H]dopamine exist in the striatum and that the low affinity system is unlikely to be found at the presynaptic nerve ending and is not due to the presence of blood vessels.