title: Short circuit current in tight and leaky epithelia.
abstract: The effect of short circuit current on the unidirectional fluxes of ions transported across tight and leaky epithelia was investigated. It was found that short circuiting of the frog gastric mucosa (classified as a tight epithelium) caused a decease of the passive JClms and a significant increase of the net Cl- secretion. However, no significant change of H+ secretory rate was observed. On the other hand, short circuiting of the mouse intestine (a known leaky membrane) caused a simultaneous increase of both Jms and Jsm fluxes of Na+ while the net fluxes of Na+ and Cl- remained unchanged. Also, short circuiting did not change the water permeability of the mouse intestine. To explain some of these results a theoretical model is presented to demonstrate that while short circuiting can block the passive ionic movement, it will cause an increase in the energy consumption of the system and introduce certain important changes in the ionic barriers and e.m.fs. The simultaneous increase in the unidirectional fluxes of Na+ under short circuit conditions can best be explained by a decrease in the polarized nature of the transepithelial shunt, thereby increasing the diffusion coefficient of the ion(s). Such an increase is specially favorable to the Na+ rather than an anion.
mesh_terms: D000818:Animals; D001001:Anura; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism; D004553:Electric Conductivity; D004848:Epithelium / Q000378:metabolism; D005750:Gastric Juice / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D051379:Mice; D010539:Permeability; D011894:Rana pipiens; D012964:Sodium / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D002712:Chlorides; D014867:Water; D012964:Sodium