Autonomic regulation of tight junctional permeability in the rat submandibular gland

The permeability of tight junctions to tracers having different molecular weights was investigated in the submandibular gland of rats stimulated parasympathetically, sympathetically, or both. Lactoperoxidase (82,000 daltons), horseradish peroxidase (40,000 daltons), and microperoxidase (1,630 daltons) were used as the tracers. The tracers were administered by close arterial infusion via the glandular artery, and their secretion into the saliva was quantified biochemically, and their secretory routes within the gland were determined histochemically at the electron microscopic level. Microperoxidase and horseradish peroxidase passed into the saliva by electrical stimulation of either the chorda or superior cervical ganglion, and the combined stimulation of both caused a larger output of both tracers. No output of lactoperoxidase into the saliva occurred with any type of nerve stimulation. Electron microscopic histochemical observations showed that molecules of molecular weight equal to or lower than that of horseradish peroxidase entered the lumen through the tight junctions between adjacent acinar cells following combined stimulations of chorda and superior cervical ganglion. These findings indicate that electrical stimulation of parasympathetic and sympathetic nerves causes an increase in tight junctional permeability of acinar cells to microperoxidase and horseradish peroxidase. Although the combined stimulation of parasympathetic and sympathetic nerves resulted in increased junctional permeability to these tracers, the junctions remained impermeable to larger molecules, i.e., lactoperoxidase.