CHOLINERGIC STIMULATION OF LACTOFERRIN AND EPIDERMAL GROWTH-FACTOR SECRETION BY THE HUMAN LACRIMAL GLAND

The human lacrimal gland produces tear proteins, such as lactoferrin a nd epidermal growth factor (EGF), that have presumed biologic activity on the ocular surface. We hypothesized that secretion of these tear p roteins by the lacrimal gland is neurally mediated. To test this hypot hesis, we evaluated the secretion of lactoferrin and EGF from the huma n lacrimal gland (LG) after cholinergic stimulation. Human LG biopsies from two donors were sliced into sections weighing similar to 100 mg and were serially placed in wells containing Dulbecco's modified Eagle 's medium (DMEM/F12; with or without atropine), followed by media alon e, media containing carbamylcholine chloride (carbachol), and then med ia alone, each for 10 min. Supernatants were then assayed for lactofer rin and EGF by antibody sandwich enzyme-linked immunosorbent assay (EL ISA). Both sets of LG explants showed statistically significant increa ses in supernatant concentrations of lactoferrin and EGF 10 min after cholinergic stimulation. These returned to prestimulation concentratio ns by 20 min. Atropine-pretreated explants showed no significant chang e in supernatant concentrations of these proteins after carbachol stim ulation. The results of these studies indicate that cholinergic stimul ation of the human LG results in increased secretion of the tear prote ins lactoferrin and EGF, This suggests that the LG can respond to the ocular surface environment by increasing secretion of biologically act ive tear constituents through neural stimulation.