TRANSFERRIN, ONE OF THE MAJOR VITREOUS PROTEINS, IS PRODUCED WITHIN THE EYE

Transferrin occurs in the vitreous at a higher relative concentration than found in the plasma or in the aqueous humor. This has been relate d to a possible local synthesis of transferrin by some component of th e eye, although convincing evidence for this has not been available. R ecently, the intraocular synthesis of several vitreous glycoproteins, possibly by the ciliary body, was demonstrated by our group. This pape r reports experiments that characterize vitreous transferrin as one of these glycoproteins. Vitreous of rabbits injected intravitreally eith er with H-3-fucose or H-3-tyrosine and killed 40 hr after the injectio n was processed for ID and 2D-electrophoresis, followed by immunoblot techniques or fluorography. Tt was possible to detect a labeled polype ptide with the same molecular weight and pi of rabbit plasma transferr in. Furthermore, this labeled polypeptide could be specifically eluted from columns of Sepharose conjugated with antibody against rabbit pla sma transferrin. Thus, these results demonstrate that at least part of the transferrin of the vitreous is synthesized within the eye.