Production of Endothelin 1 by Cultured Bovine Retinal Endothelial Cells and Presence of Endothelin Receptors on Associated Pericytes

Endothelinlike immunoreactivity was detected by radioimmunoassay in medium conditioned by cultured endothelial cells obtained from bovine retinal microvessels (9.2 ± 6.5 pM, n = 4). Sephadex G-25 column chromatography and fast-protein liquid chromatography revealed that most of the endothelinlike immunoreactivity was eluted in an identical position to synthetic endothelin 1. Retinal capillary pericyte-conditioned medium contained 2.9 pM endothelinlike immunoreactivity. In contrast to endothelial cells, retinal pericytes were found to bind endothelin. The dissociation constant and binding capacity were 0.14 nM and 1.5 × 10⁵ sites/cell (n = 3), respectively. These findings suggest that endothelin produced by the retinal endothelial cells binds to the pericytes, adding support to the suggestion that pericytes in the retina may have a musclelike function.