Epinephrine synthesis by rat arteries.
Carotid artery and aorta homogenates synthesized epinephrine (E) from norepinephrine (NE) in the presence of S-adenosylmethionine. Aorta synthesized epinine by the N-methylation of dopamine (DA) about 3 times as well as it synthesized E from NE. In contrast, adrenal homogenates which contain phenylethanolamine N-methyltransferase (PNMT) methylated DA only 1% as well as NE. The PNMT inhibitor SKF 29661 had no significant effect on methylation of NE by aorta but inhibited adrenal PNMT by 88%. N-Methylating activity in arterial homogenates was increased by dexamethasone and following catecholamine depletion by 6-hydroxydopamine (6-OHDA) and reserpine. Nine days after adrenal demedullation blood E levels collected at decapitation were less than 7% of levels found in sham operated controls but artery homogenate E was unchanged. Demedullated rats given 6-OHDA followed by reserpine for 4 days also had unchanged arterial E levels despite arterial NE levels that were less than 15% of controls. We conclude that arteries synthesize E in vitro and appear to synthesize E in vivo using an extraneuronal N-methyltransferase. This enzyme differs from adrenal PNMT in substrate and inhibitor specificity and its activity is enhanced by catecholamine depletion and by glucocorticoid treatment.
Kennedy
B
B
Department of Medicine, University of California San Diego Medical Center 92103.
Elayan
H
H
Ziegler
M G
MG
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism*; D002339:Carotid Arteries / Q000187:drug effects / Q000378:metabolism*; D002395:Catecholamines / Q000097:blood; D004837:Epinephrine / Q000096:biosynthesis*; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012436:S-Adenosylmethionine / Q000494:pharmacology
D002395:Catecholamines; D012436:S-Adenosylmethionine; D004837:Epinephrine