Abstract
1. In the isolated rat heart perfused with various concentrations of (±)-3H-noradrenaline (3H-NA) the addition of phenoxybenzamine, cocaine or desipramine to the perfusion medium resulted in an inhibition of 3H-NA uptake which appeared on kinetic analysis to be of a competitive nature.
2. Phenoxybenzamine also blocked the formation of labelled metabolites of 3H-NA in the heart at all perfusion concentrations of 3H-NA; this effect appeared to be unrelated to the inhibition of the neuronal uptake of NA produced by phenoxybenzamine, since no blockade of 3H-NA metabolism was produced by cocaine in similar experiments.
3. In slices of rat vas deferens incubated with various concentrations of 3H-NA, cocaine and desipramine and phenoxybenzamine were also shown to act as competitive inhibitors of NA uptake. Cocaine and phenoxybenzamine were less potent inhibitors of uptake in the vas deferens than they were in the heart; desipramine was equally potent in both tissues.
4. When vas deferens slices were incubated in a medium containing phenoxybenzamine for 30 min before the addition of 3H-NA, the resulting inhibition of 3H-NA uptake was increased and changed to a non-competitive type of interaction.
5. In hearts or vasa deferentia taken from animals pretreated in vivo with phenoxybenzamine (20 mg/kg), a significant inhibition of 3H-NA uptake was found when the tissues were exposed to low concentrations of 3H-NA but not when higher concentrations of 3H-NA were used.
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Selected References
These references are in PubMed. This may not be the complete list of references from this article.
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