An immunohistochemical study of secretagogue-induced secretion of epidermal growth factor in the submandibular salivary glands of mice.

Routine histological and indirect immunofluorescence techniques were used to examine the histological details of changes in the distribution of epidermal growth factor (EGF) in the submandibular salivary glands of mice during secretion. Comparisons were made bewteen glands of normal mice and those of mice given one of a number of secretagogues at various times prior to sampling. Normal submandibular salivary glands in male mice had an extensive system of convoluted granular tubules (CGT), the cells of which contained EGF. When adrenaline of alpha-phenylephrine was administered, the CGT cells degranulated, and there was a concomitant loss of intracellular EGF-positive immunofluorescence. The excretory ducts were engorged with immunofluorescent material, indicating secretion of EGF into saliva, while the ductal cells themselves remained EGF-negative. The degranulation response could be blocked by phentolamine, but not by propranolol, and no changes in EGF distribution followed the administration of pilocarpine. It was concluded that EGF is secreted, at least partly into the saliva, following an alpha-adrenergic response, and that this occurs with degranulation of the cells of the CGT.