The enhancement of retinal adhesiveness by ouabain appears to involve cellular edema

Our previous work showed that ouabain increases retinal adhesion to the retinal pigment epithelium, but the mechanism of this effect has been unclear. In this study, we have found that the ouabain-induced increase in retinal adhesiveness was blocked reversibly by removing sodium from the medium or by exposure to hyperosmotic solution. Hyposmotic solution slowed down the postmortem failure of adhesion. Tissue edema could not be documented histologically, but retinal tissue water content increased by 2.9% after exposure to ouabain. These data suggest that the ouabain effect involves cellular edema, which may enhance adhesion by tightening the interdigitation between photoreceptor outer segments and retinal pigment epithelial microvilli.