Transferrin production by the ciliary body of rabbits: a biochemical and immunocytochemical study

We have previously reported that transferrin is one of several glycoproteins synthesized within the eye and secreted into the vitreous. The present investigation was designed to determine the role of the ciliary body in the production of this vitreous transferrin.

Isolated ciliary body-iris were incubated with 3H-fucose, 3H-tyrosine or 35S-methionine and afterwards the culture media were processed for affinity chromatography using columns of Sepharose conjugated with antibody to rabbit plasma transferrin. Reverse transcription-polymerase chain reaction (RT-PCR) was carried out using total RNA extracted from fresh ciliary body-iris and primers constructed on the basis of the known sequence of transferrin mRNA from rabbit liver. The fragment obtained was employed as a probe in northern-blots of total RNA of ciliary body-iris. Furthermore, paraffin sections of eyes were treated for immunocytochemical visualization of transferrin.

A labeled polypeptide, specifically eluted from the antitransferrin columns, was detected in the incubation medium, transferrin mRNA was found in extracts of whole ciliary body-iris, and transferrin antigenicity was identified in the ciliary and iridial epithelial cells by immunocytochemistry.

These results demonstrate the ciliary epithelium as one of the sources of the vitreous transferrin.