Knauf H, Lubcke R, Kreutz W, Sachs G
Am J Physiol. 1982 Feb;242(2):F132-9. doi: 10.1152/ajprenal.1982.242.2.F132.
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.
据推测，大鼠下颌下唾液腺导管上皮细胞对Na⁺、K⁺、Cl⁻和HCO₃⁻的转运是由于基底外侧Na⁺-K⁺-ATP酶与管腔膜和基底外侧膜中的各种离子转运系统偶联所致。Na⁺重吸收取决于生电（Na⁺电导）和电中性（Na⁺:H⁺交换）途径的存在，这两种途径均对氨氯吡脒敏感。据推测，K⁺分泌是由K⁺:H⁺反向转运介导的，Na⁺重吸收与K⁺分泌之间存在偶联，因此取决于局部H⁺离子浓度。因此，电中性Na⁺内流与K⁺外流之间的比率决定了HCO₃⁻分泌的速率。在没有Na⁺内流的情况下，尽管K⁺外流减少，但HCO₃⁻分泌增加到与K⁺分泌相等的值。在管腔中没有Na⁺的情况下维持K⁺分泌需要通过基底外侧膜的额外Na⁺进入步骤，据推测这也是由于Na⁺:H⁺交换所致。
