The paracellular component of water flow in the rat submandibular salivary gland.
1. The pathway of water flow during salivary secretion by the isolated, perfused rat submandibular gland was examined using a family of homologous radiodextran molecules as probes of paracellular fluid transfer. 2. The secretion/perfusate ratio (S/P) of the secreted probes versus molecular radius during fluid secretion evoked by ACh could be resolved into two components: one that fitted a free-diffusion (Stokes-Einstein) curve and indicated diffusion through large channels, and a convective component that was linearly related to radius. 3. The convective component had a cut-off point at 0.5 nm (5 A) radius and an S/P intercept of near 1.0 at the radius of water, which indicates that most of the volume flow was paracellular. 4. The nature of such a paracellular flow is discussed together with the possible integration of this volume flow with the cellular transport of ions, resulting in an isotonic primary secretion from the gland.
Murakami
M
M
Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444, Japan.
Shachar-Hill
B
B
Steward
M C
MC
Hill
A E
AE
D000818:Animals; D001834:Body Water / Q000378:metabolism*; D002199:Capillary Permeability; D004730:Endothelium, Vascular / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012463:Saliva / Q000378:metabolism; D013363:Submandibular Gland / Q000098:blood supply / Q000166:cytology / Q000378:metabolism*