We studied the effects of PDGF-BB on changes in the diameters of murine lymph vessels with or without intact endothelium. PDGF-BB induced dilation of the lymph vessels with endothelium. Pretreatment with l-NAME or removal of the endothelium caused a significant attenuation in the PDGF-BB-induced dilation. PDGF-BB also produced dose-related reduction of the diameters of the lymph vessels without endothelium. To evaluate intracellular signal transduction and Ca(2+) -dependence of the PDGF-BB-induced tonic contraction, we investigated the effects of imatinib, GW5074 (an inhibitor of Raf-1 kinase), U-73122 (an inhibitor of phospholipase C), and xestospongin C on the PDGF-BB-induced reduction responses. All of these inhibitors caused a significant attenuation in the PDGF-BB-induced reduction response that was significantly decreased by treatment with Ca(2+) -free Krebs-bicarbonate solution or nifedipine. Higher concentrations of PDGF-BB produced a marked reduction of lymph vessel diameter within both high K(+) Krebs-bicarbonate solution and Ca(2+) -free high K(+) Krebs solution containing 1mM EGTA. These findings suggest that PDGF-BB induced endothelium-dependent NO-mediated relaxation of lymphatic smooth muscles in murine lymph vessels. PDGF receptor β-mediated tonic contraction of the muscles through increased Ca(2+) influx through the membrane and the release of membrane-bound and intracellular Ca(2+) .
© 2011 John Wiley & Sons Ltd.