Effects of the selective beta 2-adrenergic agonists, procaterole and terbutaline, on protein secretion by rat...

We examined the secretory effects of two beta 2-adrenergic agonists, procaterole and terbutaline, on the submandibular glands of anesthetized rats. After stimulation with these agents with and without a range of antagonists (non-specific alpha- and beta-adrenergic blockers), submandibular saliva was collected. The flow rate, protein concentration, the electrophoretic patterns, and amino acid composition of saliva were examined. These parameters were compared with their counterparts in saliva stimulated with isoproterenol (IPR), with and without antagonists. Assessed by these criteria, secreted proteins were classified as the alpha- or beta-type. In addition, IPR-stimulated proteins were compared in submandibular saliva of rats chronically treated with IPR or procaterole. Both beta 2-agonists were potent secretagogues for the submandibular glands of rats. All beta-antagonists completely abolished the secretory effects elicited by both beta 2-agonists, with the exceptions of carteolol and propranolol. However, no blocking agent abolished the secretory effects of IPR (60 mg/kg). The types of proteins in all submandibular saliva samples elicited by both beta 2-agonists with and without antagonists were the beta-type. Enlargement of the submandibular glands was not observed in rats subjected to chronic administration of procaterole, nor were abnormal and additional proteins observed, as confirmed by electrophoresis and by the amino acid analyses.