Fluid and protein secretion by the submandibular glands of weanling rats in response to different doses of various adrenergic agonists.

Abstract

The present study was designed to determine whether the submandibular glands of weanling rats respond to α1-and β-adrenoceptor agonists in the same manner as glands from adult animals, to determine the doses of these agonists, which give the maximum responses, and using isoelectric focusing and twodimensional electrophoreses, to determine whether proteins in submandibular saliva are modified posttranslationally as they pass through the duct systems. All of the agonists used were potent sialogogues and were given i.p. over a wide range of doses. The volumes of saliva, the total output of protein and the relative activity of protease progressively increased with increasing doses of each agonist. The optimal dose of each agonist was neither low nor excessively high. The submandibular glands of weanling rats seem to be as fully developed for fluid and protein secretion as those of adult rats. In addition, no special protein was involved in saliva secreted by the submandibular glands of weanling rats at any of the doses of the various agonists used here. However, some proteins in submandibular saliva of 25-or 35-day-old rats, when compared with extracts of the submandibular gland, appeared to have been modified posttranslationally or degraded by proteases while passing through the duct systems of the submandibular glands of weanling rats.