RT Journal Article SR Electronic T1 INCREASED BIOSYNTHESIS OF CARDIAC NOREPINEPHRINE AFTER HYPOPHYSECTOMY JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 102 OP 107 VO 165 IS 1 A1 LEWIS LANDSBERG A1 JACQUES de CHAMPLAIN A1 JULIUS AXELROD YR 1969 UL http://jpet.aspetjournals.org/content/165/1/102.abstract AB 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. © 1969, by The Williams & Wilkins Company