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The functional coupling of neuronal and extraneuronal transport with intracellular monoamine oxidase

  • U. Trendelenburg
  • L. Cassis
  • M. Grohmann
  • A. Langeloh
Part of the Journal of Neural Transmission book series (NEURAL SUPPL, volume 23)

Summary

“Metabolizing systems” are responsible for the quick inactivation of noradrenaline released from adrenergic nerve endings: a transport mechanism (uptake1 or uptake2) is arranged in series with the intracellular enzyme (monoamine oxidase, MAO; catechol-O-methyltransferase, COMT). In the perfused rat heart, kenzyme-values were determined, i.e., those rate constants which characterize the unsaturated intracellular enzymes. In the extraneuronal metabolizing system kcomt > kmao for noradrenaline and adrenaline, while rather similar rate constants were obtained for dopamine. However, for the neuronal deaminating system, kmao is considerably higher than kmao for the extraneuronal system. Second, in the rat vas deferens it is demonstrated that inhibition of neuronal MAO leads to very pronounced rises of the axoplasmic noradrenaline concentration—and this is again a reflection of the high activity of neuronal MAO. In a third series of experiments (with the rat vas deferens), the evidence indicates that the neuronal inward transport of substrates of MAO fails to saturate the enzyme. This is the functional consequence of the high activity of neuronal MAO. It is concluded that a) neuronal MAO activity is very high, and—as a consequence—b) axoplasmic noradrenaline levels are very low.

Keywords

Intracellular Enzyme Amine Concentration Neuronal Uptake Storage Vesicle Outward Transport 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

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Copyright information

© Springer-Verlag/Wien 1987

Authors and Affiliations

  • U. Trendelenburg
    • 1
  • L. Cassis
    • 1
  • M. Grohmann
    • 1
  • A. Langeloh
    • 1
  1. 1.Pharmakologisches InstitutUniversität WürzburgWürzburgFederal Republic of Germany

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