| Abstract | 「ABSTRACT」Etomidate has been used in clinical amesthesia because of its little effect on cardiovascular and central nervous system. There were few reports about the direct effect of etomidate on the vessels, and we investigated the vasodilatory action of etomidate on rat thoracic aortic rings with and without endothelium. Sixteen male Sprague-Dawley rats (BW 353±9 gm；mean ± SEM) were used to collect thoracic aortic rings, cut into 3 mm width segments, which were immersed in the muscle baths contained Krebs-Henseleit solution and aerated with 95 % O2- 5 % CO2. Randomly selected rings were denuded. Phenylephrine (3 × 10-7 M for endothelium intact rings, 1 × 10-7 M for denuded ones) or KCI (40 mM for intact, 30 mM for denuded) was added to contract the preparations, then etomidate (3 × 10-6 M to 3× 10-4 M) was cumulatively added to the baths. In KCI contracted rings, etomidate produced more relaxation on endothelium intact rings than denuded ones significantly at 3 × 10-6M, 1 × 10-5M, 3 × 10-5M, 6×10-5M and 1 × 10-4M(4.2±1.4% vs 0.0 ± 1.1 %, 15.0 ± 2.5 % vs 4.0 ± 1.3 %, 37.1 ± 3.5 % vs 20.3 ± 3.3 %, 58.8 ± 3.3 % vs 43.3 ± 4.4 % and 74.8 ± 2.6 % vs 64.0 ± 4.4 %, respectively；mean ± SEM). In phenylephrine contracted rings, etomidate showed more relaxation on endothelium intact rings than denuded ones at 3 × 10-6M, 1 × 10-5M, 3 × 10-5M and 6 × 10-5M (7.5 ± 1.8 % vs 2.2 ± 0.9 %, 17.5 ± 2.7% vs 7.8 ± 1.7 %, 37.4 ± 3.4 % vs 20.4 ± 2.3 % and 54.7 ± 4.3 % vs 41.7 ± 4.1 %, respectively). In conclusion, etomidate produced mixed endothelium-dependent and independent relaxation on rat thoracic aorta by nonspecific mechanism. Because of less relaxation in endothelium denuded rings, etomidate could be available safely even for patients with diabetes, hypertension or atherosclerosis. |
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