The parotid gland is the main source of human salivary epidermal growth factor

Abstract

To clarify the production of human epidermal growth factor (EGF) by different salivary glands, we measured its concentration by radioimmunoassay separately in whole saliva, in parotid gland (PG) saliva and in mixed submandibular (SMG) and sublingual gland (SLG) saliva. Also, we studied the presence of EGF in PG and SMG by immunohistochemistry. The mean (geometric) concentrations of EGF in PG saliva (2704 pg/ml, ±SEM interval 2393–3056 pg/ml, n=20) was higher (p<0.001) than in whole saliva (864 pg/ml, ± 733–1019 pg/ml, n=29), which in turn was higher (p<0.001) than in mixed SMG + SLG saliva (357 pg/ml, ± 296–430 pg/ml, n=16). No sex difference existed in any salivary gland EGF. Immunohistochemistry revealed EGF in the acinar cells of both PG and SMG, but only in PG there were prominent EGF deposits in luminal spaces. Our data suggest that EGF is produced by both PG and SMG, but that more of it is secreted from the PG. This result is new and challenges the general view that human salivary EGF is mainly from SMG. In mouse almost all salivary EGF comes from SMG and its amount is androgen dependent. Thus there are great differences in sources and regulation of salivary EGF between man and mouse.