Ultrastructural study of the adult albino rat parotid gland with special reference to the role of stromal telocytes

ABSTRACT

The parotid glands are considered to be the most frequent sites for salivary gland tumors. The aim of this study is to shed light on the ultrastructural features of the albino rat parotid gland including the stromal telocytes. Ten adult male albino rats were used in this study; fine pieces of the parotid glands were processed for electron microscopic examination. Semithin sections were stained with toluidine blue and were examined to select the proper sites for ultrathin sections. The parotid gland parenchyma was formed of a mixture of secretory acini and ducts. The acini were composed almost exclusively of serous-secreting cells. Some acinar cells contained large lipofuscin granules. Each intralobular duct had two parts a proximal intercalated part and a distal striated part. Over most of the length of the intercalated duct, the cytoplasmic organelles were scanty and poorly developed. Near the striated portion, the epithelial cells became taller and richer in mitochondria. Rare dark cells with many processes projecting from their lateral surfaces were observed. Small cells with a characteristic dendritic morphology were frequently observed within the epithelium of the ducts and between the serous acini. Stromal telocytes had very long and thin moniliform prolongations [telopodes] that showed thin segments [podomeres] alternating with dilatations [podoms] rich in caveolae. Telocytes created a network with the blood and lymphatic capillaries. Elements of this network were probably interacting with other cell types. These interactions were achieved either by direct contact or mediated through shedding of microvesicles. Telocytes were detected in the interacinar and the periductal stroma outside the basal lamina; they might be involved in intercellular signaling. This would indicate that these cells might modulate the parotid function