Nitric oxide-mediated inhibition of phenylephrine-induced contraction in response to hypothermia is partially modulated by endothelial Rho-kinase
Soo Hee Lee, Seong‐Ho Ok, Raghavendra Baregundi Subbarao, Ji‐Yoon Kim, Sung Il Bae, Yeran Hwang, Seongyeong Tak, Ju‐Tae Sohn
Abstract
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 (33C), wortmannin, N -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 33C. Wortmannin did not significantly alter the L-NAME-induced enhancement of phenylephrine-induced maximal contraction of endotheliumintact aortae pretreated at 33C. 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.