Fig. 1. Deletion of Cx37 or Cx40 reduces the levels of non-ablated connexins in aortic endothelium. (A) Immunoblots of alkaline-extracted endothelial cell membranes isolated from thoracic aortas of 6-7-week-old and 4-6-month-old mice. Pooled membranes from six aortas were loaded in each lane. Densitometric quantification of all blots is presented in Table 1. Connexin levels were normalized to PECAM levels measured on the same blot. Cx37 protein was substantially reduced in aortic endothelium of Cx40^–/– mice compared with wild-type levels. The drop in Cx37 was more pronounced in aortas from the younger mice (17-fold) than aortas from 4-6-month-old mice (3.0-fold). Cx40 was reduced in the endothelium of aortas from Cx37^–/– mice, but the decrease was not as large (2.6-4.2-fold). VE-cadherin and PECAM levels were not significantly altered, but caveolin-1 levels were slightly reduced in Cx37^–/– and Cx40^–/– aortic endothelium of 3-7-week-old mice. (B) Anti-Cx37 and anti-Cx40 antibodies reacted only with appropriate GST-connexin fusion proteins. (C) Cx43 was not detected in western blots of alkaline-extracted endothelial cell membranes but was detected in a similar preparation of whole aorta. (D) Chemiluminescent detection of GST-Cx37 fusion protein was linear over a 16-fold dilution range.