Indirect Evidence of Synthesis of Norepinephrine from 3-Hydroxy-Tyramine-1-C 14 in vivo. ∗

Summary

1. Formation in vivo of norepinephrine from 3-hydroxytyramine-1-C¹⁴, can be demonstrated indirectly by isolating the end product of biosynthesis, namely, 3-methoxynorepinephrine. 2. Labeled 3-methoxynorepinephrine was isolated as a diacetate derivative from urine of unstressed and stressed rats treated with iproniazid and 3-hydroxytyramine-1-C¹⁴. Radiochemical purity of the diacetate and the N-acetyl derivative was established by paper chromatography, and by recrystallization of the diacetate derivative to constant specific activity. 3. Radioactivity of 3-methoxynorepinephrine isolated from urine of rats was higher in stressed rats. 4. Labeled 3-methoxynorepinephrine continued to be excreted for 8 days after treatment with 3-hydroxytyramine-1-C¹⁴ in contrast to radioactive 3-hydroxytyramine and 3-methoxytyramine which disappeared from urine after 48 hours.

The authors thank Dr. S. Bernard Wortis for encouragement of this research, Stephen L. Chorover and Dr. Hans L. Teuber for help in stress experiments, and Linda E. Law for technical assistance.