Lang F, Messner G, Wang W, Paulmichl M, Oberleithner H, Deetjen P
Pflugers Arch. 1984 May;401(1):14-21. doi: 10.1007/BF00581527.
Inhibition of basolateral Na+/K+ ATPase by ouabain eventually abolishes transport of glucose. The present study was performed to test, if this effect is due to a dissipation of the electrochemical gradient for sodium or due to a regulatory inhibition of sodium-coupled glucose entry across the luminal membrane at increasing intracellular sodium activity. To this end, proximal convoluted tubules of the doubly perfused isolated frog kidney were perfused alternatively with solutions containing either 5 mmol/l glucose or raffinose. The potential difference across the peritubular cell membrane (PDpt) and across the epithelium (PDte) has been recorded with conventional and across the peritubular cell membrane with ion selective microelectrodes (PDpt). In the absence of luminal glucose PDpt is (+/- SEM) -54.0 +/- 2.4 mV, PDte = -1.2 +/- 2.0 mV and PDNapt = -96 +/- 5 mV. The electrochemical gradient for sodium (mu Na+) amounts to 95 mV and intracellular sodium activity to 14 mmol/l (extracellular sodium activity is 74 mmol/l). Luminal application of glucose leads to a rapid depolarisation of PDpt (delta PDpt = 8.6 +/- 0.9 mV and PDNapt (delta PDNapt = 11.1 +/- 3.0 mV) and to hyperpolarisation of PDte (delta PDte = -0.8 +/- 0.2 mV). The peritubular application of ouabain leads to a gradual, reversible and proportional decline of PDpt, PDNapt and mu Na+. Glucose induced delta PDpt and delta PDNapt decrease in parallel to PDpt and PDNapt, resp. In a separate series, the lumped conductance (Gm) of the luminal and basolateral cell membrane has been determined, which amounts to 2.4 +/- 0.3 microS/mm (tubule length). Gm decreases 23 +/- 4%, when PDpt is decreased to half.(ABSTRACT TRUNCATED AT 250 WORDS)
哇巴因对基底外侧钠钾ATP酶的抑制最终会消除葡萄糖的转运。本研究旨在测试这种效应是由于钠的电化学梯度消散，还是由于细胞内钠活性增加时对钠偶联葡萄糖跨管腔膜进入的调节性抑制。为此，对双灌注分离蛙肾的近端曲管交替灌注含5 mmol/l葡萄糖或棉子糖的溶液。用传统方法记录跨肾小管周围细胞膜（PDpt）和跨上皮细胞（PDte）的电位差，并用离子选择性微电极记录跨肾小管周围细胞膜的电位差（PDpt）。在无管腔葡萄糖的情况下，PDpt为（±标准误）-54.0±2.4 mV，PDte = -1.2±2.0 mV，PDNapt = -96±5 mV。钠的电化学梯度（μNa+）为95 mV，细胞内钠活性为14 mmol/l（细胞外钠活性为74 mmol/l）。管腔应用葡萄糖导致PDpt快速去极化（δPDpt = 8.6±0.9 mV，PDNapt（δPDNapt = 11.1±3.0 mV），并导致PDte超极化（δPDte = -0.8±0.2 mV）。肾小管周围应用哇巴因导致PDpt、PDNapt和μNa+逐渐、可逆且成比例下降。葡萄糖诱导的δPDpt和δPDNapt分别与PDpt和PDNapt平行下降。在另一个系列中，测定了管腔和基底外侧细胞膜的总电导（Gm），其值为2.4±0.3 μS/mm（小管长度）。当PDpt降至一半时，Gm下降23±4%。（摘要截断于250字）
