부산대학교 도서관

CORRECTION TO:: British Journal of Pharmacology (2003) 140, 1261-1271. doi:10.1038/sj.bjp.0705556 1: We have compared the effects of ouabain on the maintenance of gap junctional communication in rat aortic A7r5 smooth muscle cells, monkey COS-1 fibroblasts and human HeLa epithelial cells. 2: Ouabain (1?mM) interrupted dye coupling between confluent A7r5 cells within ~1?h, and high concentrations of ouabain were similarly required to reduce coupling between COS-1 cells selected to express the rat a1 Na+/K+-ATPase subunit, which is ouabain resistant. By contrast, low concentrations of ouabain (1-10?µM) attenuated dye transfer in wild-type COS-1 and HeLa cells, whose endogenous a1 subunits possess relatively high affinity for the glycoside (Ki~0.3 vs ~100?µM) Ouabain-induced reductions in dye transfer therefore correlated with the ability of the glycoside to bind to the Na+/K+-ATPase isoenzymes expressed in these different cell lines. 3: No consistent relationship between inhibition of intercellular dye transfer and secondary changes in [Ca2+]i or pHi could be identified following incubation with ouabain. 4: In separate experiments, the effects of ouabain on real-time trafficking of connexin (Cx) protein were monitored by time-lapse microscopy of A7r5 cells transfected to express a fluorescent Cx43-green fluorescent protein (GFP) and the ability of the glycoside to modulate endogenous expression of Cx40 and Cx43 evaluated in A7r5 cells by immunochemical and Western blot analysis. 5: Ouabain (1?mM) depressed vesicular trafficking of Cx43-GFP after ~1?h, and caused a time-dependent loss of endogenous Cx40 and Cx43 protein that was first evident at 2?h and almost complete after 4?h. These effects of ouabain on Cx expression were reversed ~90?min following washout of the glycoside. 6: We conclude that ouabain exerts biphasic effects on intercellular communication that involve an initial decrease in gap junctional permeability followed by a global reduction in the expression of Cx protein. Further studies are necessary to establish to what extent these actions of ouabain reflect inversion of the normal [Na+]i/[K+]i ratio and/or conversion of the Na+/K+-ATPase into a general signal transducer that regulates downstream protein synthesis.British Journal of Pharmacology (2004) 141, 374-384. doi:10.1038/sj.bjp.0705671 [ABSTRACT FROM AUTHOR]