Different responses of choriocapillary endothelial cells and retinal capillary endothelial cells to mitogenic and...

The responses of choriocapillary endothelial cells (CCE) and retinal capillary endothelial cells (RCE) in culture, in terms of phosphoinositide (PI) breakdown and cellular mitogenesis, to retinal pigment epithelial cell (RPE)-conditioned medium and vasoactive agents have been compared. RPE-conditioned medium did not induce PI breakdown in either type of cell. However, it stimulated DNA synthesis in CCE but not in RCE. Bradykinin (BDK) acted as both a fast signaling and a slow mitogenic factor on CCE, but BDK did not affect PI turnover or DNA synthesis in RCE. In contrast, thrombin stimulated PI turnover in RCE but not in CCE, though it did not induce 3H-thymidine incorporation into either type of cell. These differences in cellular functions between CCE and RCE following stimulation suggest that induction of DNA synthesis and receptor-mediated PI turnover by external factors is determined, at least in part, by the origin of the capillary endothelial cell. Therefore, extrapolation to CCE pathophysiology from experiments using endothelial cells from other capillary origins may not be valid.