ENHANCEMENT OF H3-NOREPINEPHRINE UPTAKE IN RAT TISSUES BY O-METHYLATED METABOLITES OF CATECHOLAMINES

¹ Laboratory of Clinical Science, National Institute of Mental Health. National Institutes of Health, Bethesda, Maryland

Pretreatment with metanephrine, normetanephrine or 3-methoxy-4-hydroxyphenylethylamine markedly increased the accumulation of H³-norepinephrine in the salivary glands and vas deferens of rats after the intravenous injection of the labeled catecholamine. This effect was not found in the heart, spleen, liver or uterus. The effect of treatment with the methoxyamines appears to be due to an increased initial uptake of norepinephrine. Pretreatment with methoxyamines did notelevate or prolong blood levels of H³-norepinephrine or interfere with the metabolism of the catecholamine; the subcellular distribution of H³-norepinephrine was normal in salivary glands of treated animals. The increased accumulation of H3-norepinephrine appeared to be due to an uptake into sympathetic nerves since the effect was almost completely abolished by postganglionic sympathetic denervation of the salivary gland. The ability of the normally occurring metabolite, normetanephrine, to increase the uptake of norepinephrine into sympathetic nerves in certain tissues may mean that this compound plays some modulating role in adrenergic transmission.

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