TY - JOUR T1 - THE UPTAKE AND METABOLISM OF <sup>3</sup>H-<em>l</em>-AND <sup>3</sup>H-<em>dl</em>-NOREPINEPHRINE BY INTACT RABBIT AORTA AND BY ISOLATED ADVENTITIA AND MEDIA JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 210 LP - 226 VL - 190 IS - 2 AU - Jerome A. Levin Y1 - 1974/08/01 UR - http://jpet.aspetjournals.org/content/190/2/210.abstract N2 - Rabbit thoracic aorta was separated into adventitia and media in vitro. More than 95% of the endogenous norepinephrine (NE) was found in the adventitia. Microscopic examination revealed: 1) numerous fluorescent adrenergic nerve fibers in the isolated adventitia, but none in the isolated media; 2) no adventitia adhered to the isolated media: and 3) some smooth muscle cells and fibroblasts were in the isolated adventitia. Pieces of intact aorta, adventitia and media were incubated with 3H-l-NE in Krebs' solution. All five major metabolites of 3H-l-NE accumulated in both the tissue and the incubation solution for 30 to 60 minutes. Afterwards the tissue levels remained constant presumably because the metabolites passed into the incubation solution at the same rate as they were formed. After a 30-minute incubation with 3H-l-NE, about 90% of the total glycols formed were present in the incubation solution; this figure was 80% for normetanephrine and 30 to 70% for the acidic metabolites of NE. The major inetabolite formed by the media was normetanephrine whereas the adventitia formed primarily 3,4-dihydroxyphenelethyl glycol. Comparable amounts of O-methylated and deaminated metabolites were formed by the intact aorta. As the concentration of 3H-l-NE in the incubation solution was increased from 3 x 10-8 to 3 x 10-6 M, the formation of all five metabolites increased with no appreciable change in the proportions of each metabolite formed. In intact aorta, adventitia and media, more of the major deaminated metabolite and less of the other metabolites were formed from 3H-l-NE than from 3H-dl-NE. It is suggested that monoamine oxidase and/or aldehyde reductase may exhibit a preference for l-NE or that aldehyde dehydrogenase may be specific for d-NE. © 1974 by The Williams &amp; Wilkins Co. ER -