Immunohistochemical demonstration of epidermal growth factor in the lacrimal and submandibular glands of rats

The extraorbital and intraorbital lacrimal glands, the Harderian glands, and the submandibular glands of five rats were excised after ethanol perfusion under general anesthesia. Indirect immunohistochemistry with antibodies specific to epidermal growth factor (EGF) was performed. EGF-like immunofluorescence (EGF-LI) was shown to be present both in the lacrimal glands (extra- and intraorbital) and in the submaxillary gland. In the lacrimal glands the specific immunoreaction appeared within the lumen of the acini and the cells of the tubular ducts close to the acini. Only faint EGF-LI was observed within the acinar cells. The submandibular glands showed intense EGF-LI only in the cells of the granular convoluted tubules. The Harderian gland did not show any EGF-LI. The results strongly support the idea that the lacrimal gland is a source of EGF in tear fluid (TF). Diseases of the lacrimal gland therefore may lead to decreased concentrations of EGF in tears. This may account in part for the pathophysiology of tear deficiency syndromes and may serve as the basis of a new rationale for the external application of EGF.