TY - JOUR T1 - INCREASED BIOSYNTHESIS OF CARDIAC NOREPINEPHRINE AFTER HYPOPHYSECTOMY JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 102 LP - 107 VL - 165 IS - 1 AU - LEWIS LANDSBERG AU - JACQUES de CHAMPLAIN AU - JULIUS AXELROD Y1 - 1969/01/01 UR - http://jpet.aspetjournals.org/content/165/1/102.abstract N2 - 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 ER -