Abstract
The purpose of this study was to investigate the expression of the EGF family of growth factors and EGF receptor subtypes (ErbB1-4) present in lacrimal gland and determine the effects of these growth factors on different functions of rat lacrimal gland. RT-PCR was used to detect mRNA expression in the lacrimal gland of selected members of the EGF family of growth factors, namely EGF, transforming growth factor alpha (TGF-α), heparin-binding EGF (HB-EGF), and heregulin. The presence of ErbB receptors was investigated by immunofluorescence microscopy and western blot analysis. The effects of EGF, TGF-α, HB-EGF, and heregulin on protein secretion from lacrimal gland acini were examined using a fluorescent assay for peroxidase, a marker of protein secretion. Fura-2 tetra-acetoxymethyl ester was used to measure the effects of the growth factors on intracellular [Ca 2+] ([Ca 2+] i) in acini. MAPK activation in acini by these growth factors was also examined by western blot analysis using antibodies specific to phosphorylated p42/44 MAPK and total p42 MAPK. Rat lacrimal gland expressed EGF, TGF-α, HB-EGF, and heregulin mRNA, and all four ErbB receptors were present in the lacrimal gland as detected by western blot analyses. ErbB 1 and ErbB2 were located in basal and lateral membranes of acinar and ductal cells. The location of ErbB3 could not be determined while ErbB4 was found in ductal cells. Heregulin (10 −7 m) significantly increased protein secretion in lacrimal gland acini whereas all growth factors tested significantly increased [Ca 2+] i at 10 −7 m. TGF-α (10 −9 m), heregulin (10 −7 m), EGF (10 −7 m), and HB-EGF (10 −7 m) significantly increased the amount of phosphorylated MAPK in lacrimal gland acini. We conclude that all members of the EGF family of growth factors studied are synthesised in rat lacrimal gland, could activate all four ErbB receptors that are present in this tissue, and differentially activate lacrimal gland functions.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.