Aqueous humor-stimulated protein biosynthesis in ocular tissue fibroblast culture

Dilute concentrations of aqueous humor stimulate DNA synthesis and cell division in monolayer fibroblast culture of rabbit skin and human and rabbit Tenon's capsule. We used [35S]-methionine to study 20% aqueous humor's effect on protein biosynthesis. A non-specific stimulator, 10% fetal bovine serum, was also used for comparison. Incorporation of radioactivity into acid-precipitable material was measured in both the fibroblasts and the media containing extracellular labeled proteins. The extracellular and intracellular labeled proteins were resolved by gel electrophoresis. Both 20% aqueous humor and 10% fetal bovine serum stimulated increased incorporation of [35S]-methionine into intracellular proteins relative to control values (from fibroblasts maintained in 0.5% fetal bovine serum-supplemented medium). However, 20% aqueous humor caused only a slight increase in labeling of proteins exported into the medium, whereas 10% fetal bovine serum stimulated a several-fold increase in extracellular labeled proteins relative to control values. Gel electrophoresis of labeled proteins showed that the quantitative distribution of extracellular proteins varied depending on the growth stimulator present. We conclude that the protein biosynthesis modulation by aqueous humor differs from that by fetal bovine serum. Aqueous humor may selectively stimulate the synthesis of discrete proteins while a general stimulation occurs with fetal bovine serum.