The action of Halothane and Isoflurane in Aortic Rings of Rabbit Pretreated with LNAME (L-nitrow arginine methyl ester) and MB (methylene blue)

Kwon, Eun Jung; Lim, Sang Ho

Abstract

BACKGROUND: The action of the volatile anesthetics on various organs in the body is not well known. Since Furchgott (1980) discovered endothelium derived relaxing factor (EDRF) from endothelium, many studies have been tried. Many investigators were studied about the relationship between the EDRF and the effect of the volatile anesthetics on blood vessels too. But the effect of volatile anesthetics and the site of action on the blood vessel were still controversial. In this study, we evaluated that the effect and the action site of halothane and isoflurane on isolated aortic rings of the rabbit.
METHODS
Each of obtained thoracic aorta from rabbits (1.5~2.5 Kg) was divided into 3~5 mm sized rings, and a half of that were denuded. All of the aortic rings were preconstricted with phenylephrine 1.5 10-7 Mole in warm organ bath filled with modified Krebs' solution, and then LNAME (inhibitor of nitric oxide synthase, 3 10-4Mole) was administered to one group of aortic rings. MB (inhibitor of soluble guanylate cyclase, 2 10-5Mole) was administered to another one group and neither of LNAME nor MB was administered to the other group. And then isoflurane or halothane was administered (1~4%) to all of aortic rings. The polygraph recorded the changes of tension of aortic ring which was transmitted through the force transducer.
RESULTS
It was proved that basal EDRF was released from endothelium by the fact that intact aortic rings were more constricted after LNAME or MB administration. The intact aortic rings were constricted in all concentration of isoflurane and both intact and denuded rings were relaxed in 4% concentration of halothane.
CONCLUSION
It is concluded that isoflurane in all concentrations has an endothelium -mediated vasoconstriction and 4% halothane produced vascular relaxation directly independent of existence of the endothelium of vessel.