Fig. 9. Biocytin transfer is eliminated in Cx37^–/–Cx40^–/– aortic endothelium from E18.5 embryos and is sharply reduced in E18.5 Cx40^–/– endothelium. Biocytin was injected into endothelial cells of thoracic aortas from wild-type (A), Cx37^–/– (B), Cx40^–/– (C) or Cx37^–/–Cx40^–/– (D) E18.5 embryos. Biocytin transfer occurred equally well in Cx37^–/– and wild-type aortic endothelium. Dye-transfer was reduced by 96% in Cx40^–/– aortas and was eliminated in Cx37^–/–Cx40^–/– endothelium. Quantification is presented in Fig. 10 and Table 2. Bar, 50 µm.