CATECHOLAMINE METABOLISM IN THE DOG: COMPARISON OF INTRAVENOUSLY AND INTRAVENTRICULARLY ADMINISTERED [14C]DOPAMINE AND [3H]NOREPINEPHRINE |
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Authors: | T N Chase G R Breese Edna K Gordon I J Kopin |
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Institution: | Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, Maryland 20014 |
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Abstract: | —The urinary excretion of labelled metabolites was measured in dogs which had been injected intravenously or intraventricularly with 3H]norepinephrine or 14C]dopamine. 3H]Norepinephrine injected by either route produced more labelled 3-methoxy-4-hydroxy-phenylglycol than 3-methoxy-4-hydroxymandelic acid, as did 14C]dopamine after intravenous administration. In contrast, following the intraventricular injection of 14C]dopamine, more 14C]3-methoxy-4-hydroxymandelic acid was formed than 14C]3-methoxy-4-hydroxyphenylglycol. These observations suggest that the metabolism of exogenously-administered and endogenously-formed norepinephrine may proceed through different routes and that the predominant metabolite of norepinephrine in canine brain may be 3-methoxy-4-hydroxymandelic acid rather than 3-methoxy-4-hydroxyphenylglycol. |
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