Abstract
The ultrastructure of submandibular gland (SMG) of Bactrian camels was observed by a transmission electron microscope. Routine HE staining, special staining combined with immunohistochemistry, and immunofluorescence techniques were used to study the histochemical characteristics of the submandibular gland and the localisation and distribution characteristics of epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR). HE results showed that the submandibular gland of Bactrian camels was composed of mixed serous and mucinous acini glands. The submandibular striated duct was highly developed and connected with intercalated ducts with larger diameter. Intercalated ducts are shorter and directly connected to acini. In AB-PAS staining, it was observed that the inner wall of striated tube was strongly positive for AB staining. The distribution of the reticular fibres around the follicles and ducts of the submandibular gland is distinct, with collagen fibres distributed mainly in the periphery of the ducts and sparse collagen fibres in the periphery of the acini. Immunohistochemistry and fluorescence show that EGF is strongly positive in striated and intercalated ducts, and EGFR is weakly positive in striated and intercalated ducts. Bactrian camel SMGs secrete more acidic mucins, and EGF and EGFR were mainly secreted and play a role in the pipeline system of SMGs.