Na+/H+ exchange mechanism in the basolateral membrane of the rat enterocyte.
Basolateral membrane vesicles from rat jejunal enterocytes, especially purified of brush-border contamination, were used for Na+ uptake. The basolateral membrane vesicles are osmotically active and under our experimental conditions Na+ binding is much lower than transport. An outwardly directed proton gradient stimulates Na+ uptake at both 5 microM and 5 mM concentrations. The proton gradient effect can be inhibited completely by 2 mM amiloride and partially by either FCCP or NH4Cl (NH3 diffusion). Membrane potential effects can be excluded by having valinomycin plus K+ on both sides of the vesicles. These results suggest that there is an Na+/H+ exchanger in the basolateral membrane of rat enterocytes.
Tosco
M
M
Dipartimento di Fisiologia, Facoltà di Farmacia, Università di Milano, Italy.
Orsenigo
M N
MN
Esposito
G
G
Faelli
A
A
D000641:Ammonia / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology* / Q000648:ultrastructure; D002469:Cell Separation / Q000379:methods; D004848:Epithelium / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007583:Jejunum / Q000502:physiology*; D008871:Microvilli / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D009994:Osmolar Concentration; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000641:Ammonia; D012964:Sodium