Abstract
The uptake of DL-H3-norepinephrine and H3-dopamine has been examined in rat brain homogenates. The greatest amine accumulation by particulate fractions isolated from these homogenates occurred when brains were homogenized in sucrose and incubated with Krebs-Henseleit solution. At amine concentrations ranging from 0.05 µM to 0.80 µM, catecholamine uptake was saturable in all six brain areas examined. H3-dopamine accumulation exceeded that of H3-norepinephrine at all amino concentrations. In the cerebellum, medulla oblongata-pons, midbrain, cerebral cortex and hypothalamus, the Km for H3-norepinephrine uptake was 4.0 x 10-7 M. In the striatum the Km for H3-norepinephrine uptake was 2.0 x 10-6 M, whereas the Km for H3-dopamine uptake in this area was 4.0 x 10-7 M. The K1 values for the mutual competitive inhibition of the uptake of norepinephrine and dopamine in the striatum were the same as their Km values. In areas outside the striatum, H3-dopamine was accumulated by two uptake systems, with Km values of 0.8 x 10-7 M (uptake a) and 1.4 x 10-6 (uptake b), respectively. The K1 for the inhibition of H3-norepinephrine uptake in the cerebral cortex by dopamine was identical with the Km for uptake a, indicating that this high-affinity uptake for dopamine appears to utilize the norepinephrine transport system.
Footnotes
- Received April 29, 1968.
- Accepted September 16, 1968.
- © 1969, by The Williams & Wilkins Company
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