The effects of retina-derived factors on the electrical and ultrastructural properties of the bovine pigment epithelium

The transepithelial potential (TEP) and short circuit current (SCC) of the bovine retina pigment epithelium (RPE) were monitored throughout a 3hr period. Application of retina-derived factors to the apical side of the preparation resulted in a stabilization of the TEP and SCC, followed by a secondary rise in both electrical parameters. The late, secondary rise could be eliminated or reduced by the administration of cycloheximide suggesting a dependence upon protein synthesis. The active component(s) is not heat labile and has an apparent molecular weight between 1,000-10,000. After 3 hr of incubation, both control and factor-treated RPE had normal appearing nuclei and mitochondria; however, the factor-treated preparations were significantly thicker (apical to basal membrane) and had more apical processes than the control tissues.