Rate of protein synthesis in rat salivary gland cells after pilocarpine or feeding

In untreated, fasting animals the cells of the serous demilunes of the sublingual gland incorporate 3H]-leucine at a higher rate than any other of the 5 main cell types of the 3 major salivary glands. The acinar cells of the submandibular and the mucous cells of the sublingual gland show intermediate values, while the cells of the granular ducts of the submandibular and the acini of the parotid gland have a low rate of incorporation. In fasting animals extrusion of newly synthesized protein starts early in the cells of the serous demilunes. It starts between 4 and 7 hrs after 3H]-leucine injection in the acinar cells of the submandibular gland, while the other cell types did not lose substantial amounts of labelled (glyco)protein within 7 hrs. The secretion of protein is stimulated by the cholinergic drug pilocarpine in all but one of the 5 types of salivary gland cells studied. The acinar cells of the submandibular gland react strongly, the granular duct cells less strongly. Still less are the reactions of the acinar cells of the parotid and of the nucous cells of the sublingual gland. The cells of the serous demilunes of the latter appear to be insensible to pilocarpine. The effect of food uptake on secretion does not differ from pilocarpine stimulation, with one exception: the acinar cells of the parotid gland react more strongly on food uptake than on cholenergic stimulation.