Presence and localization of neurotrophins and neurotrophin receptors in rat lacrimal gland

PURPOSE. To determine which of the neurotrophins (NTs)- nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), and neurotrophin-4/5 (NT4)- and their receptors (NTrs), TrkA, TrkB, TrkC, and p75, are present in the adult rat lacrimal gland. METHODS. RT-PCR was performed on RNA isolated from male rat lacrimal gland, using oligonucleotides specific to each NT and NTr. The presence of NT and NTr protein, was determined by Western blot analysis of lacrimal gland homogenate or membranes. The location of NTs and NTrs was determined by immunofluorescence histochemistry. Western blot analyses and immunofluorescence microscopy were performed using primary rabbit polyclonal antibodies raised against NTs and NTrs. RESULTS. RT-PCR showed positive bands at the appropriate sizes for NGF, BDNF, NT3, and NT4, and for the receptors TrkA, TrkB, TrkC, and p75. Western blot analysis confirmed these results, showing that the lacrimal gland expresses NGF, BDNF, NT3, and NT4 as well as the NTrs TrkA, TrkB, and TrkC and the p75 protein. NGF, BDNF, NT3, and NT4 were localized in the lacrimal gland acini with differing cellular distributions, whereas TrkA, TrkB, and TrkC, were localized in myoepithelial cell and ductal cell membranes. The protein p75 was expressed only on myoepithelial cell membranes. CONCLUSIONS. Members of the neurotrophin family of growth factors and their receptors are present in rat lacrimal gland, which suggests a role for NTs and their receptors in the lacrimal gland.