Kemp P J, Roberts G C, Boyd C A
Department of Human Anatomy, Oxford.
J Physiol. 1994 Apr 1;476(1):79-88.
86Rb+ was used to study potassium uptake and efflux in type II pneumocytes freshly isolated from adult guinea-pig and rat lung. Both species exhibited a substantial ouabain-sensitive component of potassium influx. In rats, most of the ouabain-resistant influx was abolished by bumetanide and removal of extracellular chloride elicited no further effect. In contrast, only a proportion of the ouabain-insensitive uptake was inhibitable by bumetanide in guinea-pigs and this species showed an additional component of influx, which was chloride dependent and which was reduced by either the K(+)-H(+)-ATPase inhibitor, omeprazole, or by the stilbene derivative, 4,4'-diisothiocyanostilbene-2,2'-disulphonate (DIDS). The chloride-dependent component was also apparent in efflux experiments in guinea-pigs, but was absent in rats. Ouabain-insensitive ATPase activity was assayed in highly purified apical membranes from guinea-pig type II pneumocytes. This activity was inhibitable by omeprazole (apparent inhibition constant, Ki, was approximately 40 microM), was potassium dependent (apparent activation constant, Ka, was approximately 200 microM) and was doubled by the addition of nigericin. While potassium transport in rat type II cells is adequately accounted for by Na(+)-K(+)-ATPase and Na(+)-K(+)-2Cl- cotransport, our data suggest the additional presence of K(+)-Cl- cotransport and K(+)-H(+)-ATPase in guinea-pig type II pneumocytes. A model of how alveolar subphase acidification may occur is proposed.
用⁸⁶Rb⁺研究从成年豚鼠和大鼠肺中新鲜分离出的II型肺泡上皮细胞对钾的摄取和外流。两种动物的钾内流均表现出大量对哇巴因敏感的成分。在大鼠中，布美他尼可消除大部分对哇巴因耐药的内流，去除细胞外氯离子则无进一步影响。相比之下，在豚鼠中，只有一部分对哇巴因不敏感的摄取可被布美他尼抑制，且该动物表现出另一种内流成分，它依赖于氯离子，可被K⁺-H⁺-ATP酶抑制剂奥美拉唑或二苯乙烯衍生物4,4'-二异硫氰基二苯乙烯-2,2'-二磺酸盐（DIDS）降低。在豚鼠的外流实验中，氯离子依赖成分也很明显，但在大鼠中不存在。在豚鼠II型肺泡上皮细胞高度纯化的顶端膜中检测了对哇巴因不敏感的ATP酶活性。该活性可被奥美拉唑抑制（表观抑制常数Ki约为40μM），依赖于钾（表观激活常数Ka约为200μM），加入尼日利亚菌素后活性加倍。虽然大鼠II型细胞中的钾转运可由Na⁺-K⁺-ATP酶和Na⁺-K⁺-2Cl⁻协同转运充分解释，但我们的数据表明豚鼠II型肺泡上皮细胞中还存在K⁺-Cl⁻协同转运和K⁺-H⁺-ATP酶。提出了一个关于肺泡亚相酸化可能如何发生的模型。
