RELATIONSHIP BETWEEN THE DISTRIBUTION OF STRESS FIBERS AND CENTROSOMES IN ENDOTHELIAL-CELLS OF THE RAT AORTA

Locomoting cells exhibit a polarity whereby certain organelles, like t he centrosome, and cytoskeletal structures, like stress fibers, are pr eferentially oriented in the direction of migration. To determine if t his was also true in endothelial cells (ECs) of the rat aorta that are migrating toward the heart, whole mounts of abdominal and thoracic ao rta were double stained with rhodamine phalloidin to label stress fibe rs and sera that labels centrosomes. Our results show that in 66% of t he ECs of the abdominal aorta where stress fibers were present, 47% ha d stress fibers on the heart side of the nucleus, 21% had stress fiber s on the side of the nucleus away from the heart, and 32% had stress f ibers across the cell. Similarly, in 50% of the ECs of the thoracic ao rta where stress fibers were present, these values were 56, 19, and 25 %, respectively. The results also showed that the centrosome was prefe rentially located toward the heart in the majority (61%) of the ECs wi th stress fibers as well as in ECs without stress fibers. Since in bot h, the same percentage of ECs had centrosomes preferentially oriented toward the heart, these results imply that while the centrosome may de termine the position of the stress fibers, the stress fibers do not ap pear to determine the position of the centrosome. Nevertheless, both c entrosomes and stress fibers in aortic ECs are preferentially oriented in the direction of migration, when they may be involved in defining the direction and providing the force for locomotion, respectively. (C ) 1997 Wiley-Liss, Inc.