Thiopental induces contraction of rat aortic smooth muscle through Ca(2+) release from the sarcoplasmic reticulum

Little is known about the mechanism of thiopental-induced contraction in vascular smooth muscle. This study aimed to clarify this question by conducting isometric tension experiments and (45)Ca(2+) flux measurements in endothelium-denuded rat aortic rings. Thiopental induced a concentration-dependen...

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Published inAnesthesia and analgesia Vol. 91; no. 1; pp. 62 - 67
Main Authors Mousa, W F, Enoki, T, Fukuda, K
Format Journal Article
LanguageEnglish
Published United States 01.07.2000
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Summary:Little is known about the mechanism of thiopental-induced contraction in vascular smooth muscle. This study aimed to clarify this question by conducting isometric tension experiments and (45)Ca(2+) flux measurements in endothelium-denuded rat aortic rings. Thiopental induced a concentration-dependent contraction under basal tension. This contraction was enhanced when rings were precontracted with phenylephrine in the presence of verapamil. In Ca(2+)-free solution, thiopental-induced contraction was reduced but not abolished with high concentrations. Ca(2+) store depletion with a maximum dose of caffeine in Ca(2+)-free solution further reduced the contraction by subsequent thiopental. Ca(2+) store depletion with thapsigargin completely abolished contraction by thiopental. (45)Ca(2+) influx experiment in the presence of verapamil showed that thiopental could not induce any Ca(2+) influx with or without phenylephrine prestimulation. The (45)Ca(2+) efflux experiment showed more evidence of thiopental-induced Ca(2+) release, which was abolished by thapsigargin. In conclusion, thiopental induces contraction in rat aortic smooth muscle by releasing Ca(2+) from the sarcoplasmic reticulum without Ca(2+) influx. This is the first study providing evidence that thiopental-induced vascular contraction is caused by Ca(2+) release from the sarcoplasmic reticulum of the smooth muscle.
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ISSN:0003-2999
DOI:10.1213/00000539-200007000-00012