Abstract
The biosynthesis of norepinephrine in the hearts of chronically hypophysectomized rats has been studied by determining the rate of incorporation of labeled precursors into catecholamines. Both C14-tyrosine and H3-dopamine, administered as a single i.v. injection, were converted more rapidly to norepinephrine in the hearts of the hypophysectomized rats than in the controls. Previous work has indicated that hypophysectomy is associated with an increased turnover of cardiac norepinephrine. The present study demonstrates that increased de novo biosynthesis of catecholamines in the heart occurs concomitantly with the increased turnover. Small changes in the in vitro activities of the enzymes which metabolize catecholamines (monoamine oxidase and catechol-O-methyltransferase) in the hypophysectomized rat were also found.
Footnotes
- Received July 29, 1968.
- Accepted September 17, 1968.
- © 1969, by The Williams & Wilkins Company
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