Iron-binding proteins in the human vitreous: lactoferrin and transferrin in health and in proliferative intraocular disorders.

Transferrin, recently detected in preretinal membranes, may contribute to cell proliferation by iron donation for mitosis. We have investigated whether lactoferrin, the second iron-binding protein of the human vitreous, could play a similar role in proliferative intraocular disorders (PID). Using immunochemistry, however, we could not label lactoferrin in surgically obtained membrane specimens from patients with idiopathic proliferative vitreoretinopathy (PVR), traumatic PVR, and proliferative diabetic retinopathy (n = 15). The amounts of both proteins in normal human vitreous, as measured by enzyme-linked immunosorbent assay, were 73.7 +/- 6.6 mg/l for transferrin but below 50 micrograms/l for lactoferrin. Transferrin was also determined in 35 vitreous aspirates from patients with PID. The highest levels were found in idiopathic PVR (846 +/- 256 mg/l), followed by proliferative diabetic retinopathy (405 +/- 121) and traumatic PVR (197 +/- 83 mg/l). A statistically significant difference between the three types of PID and physiologic vitreous, respectively, was not observed. The total vitreal protein, however, was significantly elevated in all three groups of PID.