Interrelationships of ion transport in rat submaxillary duct epithelium.
The transport of Na+, K+, Cl-, and HCO3(-) across the epithelium of the rat submaxillary salivary duct is postulated to be due to the coupling of the basolateral Na+-K+-ATPase with various ion transport systems in the luminal and basolateral membranes. Na+ reabsorption depends on the presence of a rheogenic (Na+ conductance) and an electroneutral (Na+:H exchange) pathway, both of which are sensitive to amiloride. K+ secretion is postulated to be mediated by a K+: H+ antiport, coupling between Na+ reabsorption and K+ secretion, thus depending on local H+ ion concentration. The ratio between electroneutral Na+ influx and K+ efflux, therefore, determines the rate of HCO3(-) secretion. In the absence of Na+ influx, although K+ efflux falls, HCO3(-) secretion rises to a value equal to that of K+ secretion. The maintenance of K+ secretion in the absence of luminal Na+ requires an additional Na+-entry step across the basolateral membrane, also postulated to be due to Na+:H+ exchange.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001693:Biological Transport, Active; D006859:Hydrogen / Q000378:metabolism; D066298:In Vitro Techniques; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013363:Submandibular Gland / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology
D001639:Bicarbonates; D006859:Hydrogen; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium