Abstract
Whether volatile anesthetics attenuate angiotensin II-mediated vascular tone has not been determined. The current study was designed to investigate the effects of sevoflurane on the angiotensin II-stimulated, Ca2+- and protein kinase C (PKC)-mediated contraction of rat aortic smooth muscle. The dose-dependent effects of sevoflurane on angiotensin II (10 m)-induced contraction, the increase in intracellular Ca2+ concentration, and PKC phosphorylation of rat aortic smooth muscle were measured using an isometric force transducer, a fluorometer, and Western blotting, respectively. Angiotensin II induced a transient increase in intracellular Ca2+ concentration, phosphorylation of Ca2+-dependent PKC (cPKC)-alpha, and consequently, a transient contraction of rat aortic smooth muscle. Phosphorylation of the Ca2+-independent PKC-epsilon was not detected. The angiotensin II-induced contraction was almost completely abolished by removing extracellular Ca2+ and was significantly inhibited by the selective cPKC inhibitor Gö 6976 (10 M) but was not inhibited by the nonselective PKC inhibitor Ro 31-8425 (10 M). Sevoflurane dose-dependently inhibited the angiotensin II-induced contraction, with reductions of 14.2 +/- 5.2% (P > 0.05), 26.7 +/- 8.9% (P < 0.05), and 38.5 +/- 12.8% (P < 0.01) (n = 10) in response to 1.7, 3.4, and 5.1% sevoflurane, respectively. The angiotensin II-elicited increase in intracellular Ca2+ concentration was not significantly influenced by 3.4, 5.1, or 8.5% sevoflurane. However, cPKC-alpha phosphorylation induced by angiotensin II was inhibited dose dependently by 1.7, 3.4, and 5.1% sevoflurane, with depressions of 20.5 +/- 14.2% (P > 0.05), 37.0 +/- 17.8% (P < 0.05), and 62.5 +/- 12.2% (P < 0.01) (n = 4), respectively. The current study indicates that Ca2+ and cPKC-alpha are involved in angiotensin II-induced vascular contraction. Sevoflurane dose-dependently inhibited the angiotensin II-stimulated, cPKC-mediated but not Ca2+-elicited contraction of rat aortic smooth muscle.
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