Na+, K+ and Cl- transport in isolated small intestinal cells from guinea pig. Evidences for the existence of a second Na+ pump.
Isolated small intestinal epithelial cells, after incubation at 4 degrees C for 30 min, reach ion concentrations (36 mM K+, 113 mM Na+ and 110 mM Cl-) very similar to those of the incubation medium. Upon rewarming to 37 degrees C, cells are able to extrude Na+, Cl- and water and to gain K+. Na+ extrusion is performed by two active mechanisms. The first mechanism, transporting Na+ by exchanging it for K+, is inhibited by ouabain and is insensitive to ethacrynic acid. It is the classical Na+ pump. The second mechanism transports Na+ with Cl- and water, is insensitive to ouabain but is inhibited by ethacrynic acid. Both mechanisms are inhibited by dinitrophenol and anoxia. The second Na+ extruding mechanism could be the Na+/K+/2Cl- cotransport system. However, this possibility can be ruled out because the force driving cotransport would work inwards, and because Na+ extrusion with water loss continues after substitution of Cl- by NO3-. We propose that enterocytes have a second Na+ pump, similar to that proposed in proximal tubular cells.
D000818:Animals; D002712:Chlorides / Q000378:metabolism*; D003080:Cold Temperature; D004976:Ethacrynic Acid / Q000494:pharmacology; D006168:Guinea Pigs; D000860:Hypoxia / Q000378:metabolism; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D008433:Mathematics; D009609:Nitrous Oxide / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D010042:Ouabain; D012964:Sodium; D009609:Nitrous Oxide; D004976:Ethacrynic Acid; D011188:Potassium