Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 339, Issue 4, pp 433–440

The release of3H-noradrenaline by p- and m-tyramines and -octopamines, and the effect of deuterium substitution in α-position

  • C. -L. Schönfeld
  • U. Trendelenburg


The3H-noradrenaline-releasing effects of p- and m-tyramines and -octopamines, either deuterated or not, were studied in isolated vasa deferentia of the rat (COMT inhibited and calcium-free solution in all experiments).

Km, for uptake1 was higher for octopamines than for tyramines, but not increased by the introduction of deuterium in α-position, except for (probably contaminated) deuterated p-octopamine. Other tissues were preloaded with3H-noradrenaline. After inhibition of vesicular uptake and MAO equi-releasing concentrations of the eight amines were strictly correlated withKm, they were 6 to 7 times higher for unsubstituted octopamines than for corresponding tyramines. When only MAO (but not vesicular uptake) was inhibited, this difference decreased to about 4-fold, but the releasing potency of the deuterated amines (relative to their parent amines) remained unchanged (except for p-octopamine). When vesicular uptake and MAO were intact, unsubstituted octopamines were only 1.5 to 2.2 times less potent than the corresponding tyramines. Analysis of the efflux of3H-DOPEG confirmed that this gain in the relative potencies of octopamines is due to their increased ability to mobilize vesicular 3H-noradrenaline; moreover, deuterated amines as well were then better mobilizers than were their parent amines.

It is concluded that, provided vesicular uptake is intact, the introduction of a \-OH-group enhances the ability of indirectly acting sympathomimetic amines to mobilize vesicular noradrenaline; the introduction of deuterium in α-position, on the other hand, enhances this mobilizing effect exclusively when MAO is intact.

Key words

Indirectly acting sympathomimetic amines Tyramine Octopamine Deuterium in α-position Rat vas deferens Noradrenaline outward transport 

Abbreviations used here


catechol-O-methyl transferase


dihydroxymandelic acid




monoamine oxidase


column chromatographic fraction containingall O-methylated metabolites


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Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • C. -L. Schönfeld
    • 1
  • U. Trendelenburg
    • 1
  1. 1.Institut für Pharmakologie und ToxikologieUniversität WürzburgWürzburgGermany

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