Authors developed a novel lacrimal gland (LG) duct isolation technique earlier (IOVS, 2007; 48:3746-3755) which makes possible to obtain more information on the function and regulation of LG ductal cells. The role of LG ductal epithelium on fluid secretion is unknown. The aim of the present study was to investigate LG ductal fluid secretion by means of measurement of fluid secretion evoked by different agonists.Methods
Experiments were performed on isolated rabbit LG interlobular duct segments maintained in short term culture. The ends of the ducts sealed after overnight incubation forming a closed luminal space. Fluid secretion into closed intraluminal space as swelling response was analyzed using bright field videomicroscopy technique.Results
The secretory response to carbachol or to forskolin stimulation was measured in HEPES buffered and in HCO3-/CO2- buffered solutions. Carbachol initiated ductal swelling. This result proves the cholinergic effect-evoked ductal fluid secretion. Fluid secretion was biphasic consisting of a continuous swelling in the first 5 minutes followed by a plateau phase. Secretory rates did not show a substantial difference measured in HEPES and HCO3-/CO2 -buffered solutions. In contrast to the biphasic effect of carbachol, forskolin stimulation resulted in a rapid, continuous swelling response. The secretory effect of forskolin did not differ in HEPES and HCO3-/CO2-buffered solutions.Conclusion
Fluid secretion of LG ductal cells induced by carbachol and by forskolin stimulations strongly supports the hypothesis, that LG ductal system is actively involved in lacrimal fluid secretion. Our results provide the first experimental evidence of secretory function of this epithelium.