The metabolism of epinephrine containing isotopic carbon. II.

In a previous publication (l), evidence was presented indicating that a major pathway of epinephrine metabolism involved cleavage of the molecule at some point between the P-carbon and the methyl carbon. The presence of ether-soluble substances in urine suggested that methylamine was split off, at least to some extent. A minimum of five urinary metabolites of epinephrine has been revealed by paper chromatography (2). The interpretation of these data, however, was complicated by the use of dl-epinephrine, employed because of the unavailability of the natural 1 isomer possessing adequate radioactivity. There was thus no assurance that some of these observations were not attributable to the unnatural d isomer and hence unrelated to the metabolism of physiological epinephrine. Recently we have synthesized methyl-Cl*-dl-epinephrine of higher specific activity and prepared its 1 isomer as well as the 1 isomer of /3-C’*-epinephrine. Using the two types of radioactive l-epinephrine we have confirmed previously reported metabolic studies and have found no observable differences in the fates of I-epinephrine and dl-epinephrine in the rat. Evidence is also presented to demonstrate that methylamine is split from epinephrine.