[Immunochemical detection of the proliferating cell nuclear antigen (PCNA/cyclin) in ocular tissues]

The authors developed radioimmunoassay (RIA) for proliferating cell nuclear antigen (PCNA/cyclin), which a protein synthesizes in phase with DNA, as a marker for cell replication. We used it to detect the amounts of PCNA and estimated rates of cell replication in ocular tissues (cornea, lens epithelium, retina-plus-choroid and optic nerve) and in non-ocular tissues (skin, skeletal muscle, brain, thymus, small intestine and liver) in rats. Antisera were raised in rabbits to oligopeptide fragment of human PCNA (hPCNA): the C-terminal fragment [Tyr254]-hPCNA (254-261). For RIA the synthetic peptides were used as standards and radioiodinated [125I-Tyr254]-hPCNA (254-261) as radioligands. The IC50 was 30-40 f mole/tube with a sensitivity 0.5-1.0 f mole/tube for this assay. Tissue extracts in 1 M acetic acid were digested with trypsin to release fragment (255-261) from whole PCNA and were assayed by this method. The highest amounts of immunoreactive PCNA were found in lens epithelium and skin, while the lowest amounts were found in optic nerve and muscle. The cornea showed a higher value than retina-plus-choroid or optic nerve. A high cell replication in the lens epithelium was revealed.