Endothelium dependent Effects of Halothane and Sevoflurane on Isolated Rabbit Aortic Vascular Rings

Min, Kyeong Tae; Kim, Won Oak; Nam, Soon Ho; Kim, Jong Rae; Shim, Yon Hee

Abstract

This study was aimed to elucidate the endothelium-dependent vascular effects of halothane and sevoflurane on rabbit aortic rings at two conventional concentrations(high induction and low maintenance concentration in human). Isometric tenslon was recorded in isolated aortic rings. Preparations of rabbit thoracic aorta were suspended in Krebs' buffer and aerated with 95% O2 and 5% CO2. One set of the rings had intact endothelium and the other set of the rings had endothelium mechanically denuded. In the first experiments, the rings were precontracted with norepinephrine(NE) of 10-7 M. After tension was stabilized in 10~15 minutes following NE, halothane(1, 2%) or sevoflurane(2, 4%) was bubbled with O2/CO2 gas mixture at increasing concentrations. In the second experiment, O2/CO2 gas mixture only(control rings), halothane 2% or sevoflurane 4 % with O2/CO2, gas mixture was bubbled for 10(-7) minutes prior to and during contraction with NE of 10M. After tension was stabilized following NE, acetylcholine(10(-8)-10(-6) M) was added cumulatively. In the third experiment, the procedure was as same as the second experiment except for that acetylcholine(10(-8)-10(-6) M) was substitued for nitroglycerin (10(-9)-10(-6) M) . The present study demonstated that both of halothane and sevoflurane at high concentration caused a vasoconstriction to 110.7+/-4.2% and 122.4+/-8.4% in vascular rings with intact endothelium, and 106.1+/-1.9% and 118.3+/-3.5% in vascular rings with denuded endothelium, respectively, compared to each control value of 100%. Furthermore, halothane and sevoflurane attenuated the acetylcholine induced relaxing response in NE-precontracted vascular rings with intact endothelium, but did not affect any change of tension in vascular rings with denuded endothelium. Halothane and sevoflurane did not attenuate the nitroglycerin induced relaxing response in NE-precontracted vascular rings with both intact and denuded endothelium. In conclusion, halothane and sevoflurane at high concentration has vasoconstrictory effects on vascular smooth muscles in rabbit aortic rings regardless of presence of endothelium and also attenuated the endothelium-dependent relaxation.