Na+ transport by mammalian stomach.
Gastric mucosas from newborn pigs (0--20 days) and rabbits (0--20 days) were used for in vitro investigation of active Na+ transport during resting (no HCl secretion) conditions. As measured with 22Na+, these tissues actively absorb Na+ from the mucosal-to serosal (m-t-s) bathing solution during both open-circuit and short-circuit current (Is) conditions. In the nonsecreting state, net Na+ transport accounts for 40--60% of Isc. The remaining current is provided by net s-to-m flux of Cl-. Amiloride (2-5 X 10(-5) M) in the mucosal solution abolishes this active Na+ transport by inhibiting m-to-s fluxes of Na+ (JNams). In vivo-in vitro experiments showed that active Na+ transport is a normal function of the resting mammalian stomach. Decreasing pH of the mucosal solution below pH 5 reversibly causes decreased current-generating capability of the tissue. Pretreatment of the tissue with amiloride abolishes this pH effect. The implication is that the low pH affects the Na+-entry step into cells. "Titration curves" of current vs. pH had an apparent pK approximately 4.0. Ouabain and K+-free solutions both cause decreases in active Na+ and Cl- current. Calculations indicate that a shunt may account for only a small (less than 30%) percentage of total transepithelial conductance.
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism; D004285:Dogs; D004594:Electrophysiology; D005753:Gastric Mucosa / Q000378:metabolism* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D013552:Swine
D002712:Chlorides; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D011188:Potassium