# Analysis of Histochemical Characteristics of Submandibular Gland of the Bactrian Camel

## TL;DR

This study examines the submandibular gland of Bactrian camels to understand its structure and function, particularly in adapting to desert environments.

## Contribution

The study provides new insights into the histochemical and ultrastructural features of the Bactrian camel's submandibular gland.

## Key findings

- The submandibular gland of Bactrian camels contains mixed serous and mucinous acini glands.
- EGF is strongly expressed in ducts, while EGFR is weakly expressed, suggesting a role in gland function.
- The gland secretes acidic mucins, which may help in adapting to desert forage conditions.

## Abstract

The histochemical characteristics of the submandibular gland of the Bactrian camel were analysed by the ultrastructural features of the submandibular gland, the expression and distribution of epidermal growth factor, and the epidermal growth factor receptor, which provided a basis for exploring the physiological functions of the submandibular gland of Bactrian camels. This study may provide clues for the analysis of the submandibular gland in Bactrian camels in improving the rumen microenvironment and better adapting to desert forage conditions.

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.