ETX treatment causes caveolae formation.

(A) SEM of primary BEC treated with or without 50nM of ETX for 1 hour. White arrows point to apical surface invaginations. (B) Higher magnification of surface invaginations on ETX treated BEC. (C) Vertical TEM sections of primary BEC treated with or without 50nM ETX for 2 hours. White arrows point to apical surface invaginations morphologically similar to caveolae. (D) Quantification of the number of caveolae per um of cell surface in control or ETX treated cells. Results expressed as Mean ± STDEV, *p<0.003 determined by T-Test, n = 3. (E) and (F) additional micrographs of BEC treated with 50nM ETX for 2 hours. Black arrows denote caveolae fusing into other internalized caveolae or endosomes. In some cells, large MVB are observed.