Changes in the Permeability of the Salivary Gland Caused by Sympathetic Stimulation and by Catecholamines

The permeability of the submaxillary gland of cats and dogs has been tested by determining the rates at which non-electrolytes penetrate from the plasma into the saliva. Electrical stimulation of the cervical sympathetic trunk or administration of epinephrine or norepinephrine increases the permeability of the gland enabling glucose (molecular radius, MR = 3.5 Å), sucrose (MR = 4.4 Å), raffinose (MR = 5.6 Å), polyglycol 1000 (MR = 7.2 Å), and polyglycol 1540 (MR = 8.1 Å) to penetrate into the saliva from which they are otherwise excluded. Inulin (MR = 14.7 Å) does not enter the saliva under these circumstances. Analysis of the transfer rates suggests that the molecules diffuse through a pore structure permitting free diffusion for molecules with a radius less than 5.7 Å. Close intraarterial injection of C¹⁴-glucose demonstrates that at least part of this permeability is located in the duct system of the gland. Since epinephrine does not enable sucrose to enter the cells of the gland, it appears that penetration from the extracellular space into the saliva occurs by diffusion through intercellular gaps. The characteristics of the permeability allow conclusions as to the localisation and geometry of the ultrastructural change produced.