Abstract
A partially purified preparation of norepinephrine storage particles from the rat heart was studied in vitro. The particles were found to have dopamine β-oxidase activity, indicating that norepinephrine may be formed from dopamine in the storage granules as well as taken up from the cytoplasm of the cell. ATP was found in the particles in the same molar ratio to norepinephrine as has been previously described in adrenal chromaffin granules, and could serve to form a storage complex with the amine. There were only trace amounts of catechol-O-methyl transferase and monoamine oxidase in the preparation. The particles were most stable in solutions at 4°C containing sucrose, magnesium or calcium, but retained about half their catecholamine content in sucrose at 23°C for 1 hour. Norepinephrine was released from the particles into free solution in media of low tonicity or pH, in the presence of the detergent sodium deoxycholate, and by high concentrations of reserpine, tyramine and cocaine. H3-norepinephrine was taken up from solution and concentrated 35-fold in the particles by an initial nonspecific adsorption followed by a slower temperature-dependent process. High concentrations of reserpine and tyramine inhibited this uptake.
Footnotes
- Received July 3, 1963.
- Accepted September 6, 1963.
- The Williams & Wilkins Company
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