钠/钙交换在兔肾集合系统原代培养物跨细胞钙转运中的作用。
Role of Na+/Ca2+ exchange in transcellular Ca2+ transport across primary cultures of rabbit kidney collecting system.
作者信息
Bindels R J, Ramakers P L, Dempster J A, Hartog A, van Os C H
机构信息
Department of Physiology, University of Nijmegen, The Netherlands.
出版信息
Pflugers Arch. 1992 Apr;420(5-6):566-72. doi: 10.1007/BF00374634.
Cells from connecting tubule and cortical collecting duct of rabbit kidney were isolated by immunodissection with mAb R2G9 and cultured on permeable filters. Confluent monolayers developed an amiloride-sensitive transepithelial potential difference of -50 +/- 1 mV (lumen negative) and a transepithelial resistance of 507 +/- 18 omega cm2. Transepithelial Ca2+ transport increased dose-dependently with apical [Ca2+] and, in solutions containing 1 mM Ca2+, the active transcellular Ca2+ transport rate was 92 +/- 2 nmol h-1 cm-2. Transcellular Ca2+ transport was dependent on basolateral Na+ (Nab+). Isoosmotic substitution of Nab+ for N-methylglucamine resulted in a concentration-dependent decrease in Ca2+ absorption, with maximal inhibition of 67 +/- 5%. A Hill plot of the Na(+)-dependence yielded a coefficient of 1.9 +/- 0.4, indicating more than one Na+ site on a Na(+)-dependent Ca2+ transport system. In addition, the absence of Cab2+ resulted in a significant increase in Ca2+ transport both in the presence and absence of Nab+. Added basolaterally, ouabain (0.1 mM) inhibited Ca2+ transport to the same extent as did Na(+)-free solutions, while bepridil (0.1 mM), an inhibitor of Na+/Ca2+ exchange, reduced Ca2+ transport by 32 +/- 6%. Methoxyverapamil, felodipine, flunarizine and diltiazem (10 microM) were without effect. Depolarisation of the basolateral membrane, by raising [K+]b to 60 mM, significantly decreased transcellular Ca2+ transport, which is indicative of electrogenic Na+/Ca2+ exchange. In conclusion, active Ca2+ transport in the collecting system of rabbit kidney is largely driven by basolateral Na+/Ca2+ exchange. However, a residual Ca2+ absorption of about 30% was always observed, suggesting that other Ca2+ transport mechanisms, presumably a Ca(2+)-ATPase, participate as well.
用单克隆抗体R2G9通过免疫解剖法分离兔肾连接小管和皮质集合管的细胞，并将其培养在可渗透滤膜上。汇合的单层细胞产生了对氨氯地平敏感的跨上皮电位差为-50±1mV（管腔为负），跨上皮电阻为507±18Ω·cm²。跨上皮Ca²⁺转运随顶端[Ca²⁺]呈剂量依赖性增加，在含有1mM Ca²⁺的溶液中，主动跨细胞Ca²⁺转运速率为92±2nmol·h⁻¹·cm⁻²。跨细胞Ca²⁺转运依赖于基底外侧Na⁺（Nab⁺）。用N-甲基葡糖胺等渗替代Nab⁺导致Ca²⁺吸收呈浓度依赖性降低，最大抑制率为67±5%。Na⁺依赖性的希尔图得出系数为1.9±0.4，表明在Na⁺依赖性Ca²⁺转运系统上有不止一个Na⁺位点。此外，在有或没有Nab⁺的情况下，去除Ca²⁺都会导致Ca²⁺转运显著增加。从基底外侧加入哇巴因（0.1mM）对Ca²⁺转运的抑制程度与无Na⁺溶液相同，而Na⁺/Ca²⁺交换抑制剂苄普地尔（0.1mM）使Ca²⁺转运减少32±6%。甲氧基维拉帕米、非洛地平、氟桂利嗪和地尔硫䓬（10μM）无作用。通过将[K⁺]b提高到60mM使基底外侧膜去极化，显著降低跨细胞Ca²⁺转运，这表明存在电中性Na⁺/Ca²⁺交换。总之，兔肾集合系统中的主动Ca²⁺转运主要由基底外侧Na⁺/Ca²⁺交换驱动。然而，总是观察到约30%的残余Ca²⁺吸收，这表明其他Ca²⁺转运机制，可能是一种Ca²⁺-ATP酶，也参与其中。
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