RESUMO
This study examined the possible upstream cellular signaling pathway associated with nitric oxide (NO)-mediated inhibition of phenylephrine-induced contraction in isolated rat aortae in response to mild hypothermia, with a particular focus on endothelial Rho-kinase. We examined the effects of mild hypothermia (33°C), wortmannin, Nω-nitro-L-arginine methyl ester (L-NAME), Y-27632, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and methylene blue, alone and combined, on phenylephrine-induced contraction in isolated rat aortae. Finally, we examined the effects of mild hypothermia, wortmannin, Y-27632 and L-NAME, alone and combined, on endothelial nitric oxide synthase (eNOS) and endothelial Rho-kinase membrane translocation induced by phenylephrine. Mild hypothermia attenuated phenylephrine-induced contraction only in endothelium-intact aortae. L-NAME, wortmannin, ODQ and methylene blue increased phenylephrine-induced contraction of endothelium-intact aortae pretreated at 33°C. Wortmannin did not significantly alter the L-NAME-induced enhancement of phenylephrine-induced maximal contraction of endothelium-intact aortae pretreated at 33°C. Wortmannin abolished the ability of Y-27632 to magnify the hypothermic inhibition of maximal phenylephrine-induced contraction. Wortmannin and L-NAME inhibited the enhancing effect of mild hypothermia on phenylephrine-induced eNOS phosphorylation. Y-27632 and L-NAME attenuated the enhancing effect of hypothermia on phenylephrine-induced endothelial Rho-kinase membrane translocation. The results suggest that hypothermia-induced, NO-dependent inhibition of phenylephrine-induced contraction is mediated by phosphoinositide 3-kinase and inhibited by endothelial Rho-kinase activation.
Assuntos
Aorta/metabolismo , Hipotermia Induzida/efeitos adversos , Óxido Nítrico/genética , Quinases Associadas a rho/genética , Amidas/farmacologia , Animais , Aorta/efeitos dos fármacos , Aorta/crescimento & desenvolvimento , Aorta/patologia , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/metabolismo , Humanos , Contração Muscular/efeitos dos fármacos , Contração Muscular/genética , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase Tipo III/genética , Fenilefrina/farmacologia , Fosfatidilinositol 3-Quinases/genética , Fosforilação/efeitos dos fármacos , Piridinas/farmacologia , Ratos , Transdução de Sinais/efeitos dos fármacos , Vasoconstrição/genéticaRESUMO
The goal of this study was to examine the effect of lipid emulsion on the vasodilation induced in isolated endothelium-denuded rat aortae by a toxic dose of amlodipine. We examined the effects of lipid emulsion and verapamil on amlodipine-induced vasodilation. We also examined the effects of a mixture of lipid emulsion and amlodipine, as well as the centrifuged aqueous extract (CAE) obtained by ultracentrifuging such a mixture and then removing the upper lipid layer, on amlodipine-induced vasodilation. The effect of lipid emulsion on the amlodipine concentration was examined. Lipid emulsion attenuated amlodipine-induced vasodilation in isolated aortae. Both CAE and lipid emulsion containing amlodipine inhibited amlodipine-induced vasodilation. However, there was no significant difference in amlodipine-induced vasodilation between aortae treated with CAE and those treated with lipid emulsion containing amlodipine. Verapamil inhibited amlodipine-induced vasodilation. Lipid emulsion decreased the concentration of amlodipine. Lipid emulsion attenuated the vasodilation induced by a toxic amlodipine dose in NaF-precontracted aortae. The data show that lipid emulsion inhibited the vasodilation induced by a toxic amlodipine dose in isolated rat aortae by reducing the concentration of amlodipine. Amlodipine-induced vasodilation seems to be mediated mainly by blockade of L-type calcium channels and partially by inhibition of the Rho-kinase pathway.
