Venning M G, de la Lande I S
Department of Clinical and Experimental Pharmacology, University of Adelaide, Australia.
Blood Vessels. 1988;25(5):232-9. doi: 10.1159/000158735.
Rabbit ear arteries were perfused extraluminally or intraluminally with noradrenaline (NA) 0.18 mumol/l for 30 min. The extraluminal NA taken up was largely accumulated in the artery; 3,4-dihydroxymandelic acid (DOPEG) and normetanephrine (NMN) were the principle metabolites. The intraluminal NA taken up was largely O-methylated to NMN, the formation of NMN exceeding that from extraluminal NA by a factor of 2.6; DOPEG was formed in trace amounts only. Sympathectomy eliminated DOPEG formation and abolished the influence of the surface of entry on O-methylation by selectively increasing NMN formation from extraluminal NA without affecting the formation from intraluminal NA. Cocaine (30 mumol/l) was without effect on metabolite formation from extraluminal NA in sympathectomized arteries. The results (a) confirm earlier evidence obtained on reserpinized arteries which indicated that the sympathetic nerves play an important role in the disposition and metabolism of NA only when the amine enters via the adventitial surface, and (b) argue against the possibility that cocaine exerts an extraneuronal action on metabolism of NA in this vessel.
