Humes H D, Sastrasinh M, Weinberg J M
J Clin Invest. 1984 Jan;73(1):134-47. doi: 10.1172/JCI111184.
The divalent cations, Ca++ and Mg++, are known to competitively inhibit a large number of aminoglycoside-membrane interactions, so that Ca++ prevents both the neurotoxic and ototoxic effects of these antibiotics acutely in vitro. Since gentamicin-induced plasma and subcellular membrane damage appear to be critical pathogenetic events in gentamicin nephrotoxicity, Ca++ may play a similar protective role in gentamicin-induced acute renal failure. To test this possibility in vivo, rats (group 2) were given a 4% calcium (in the form of CaCO3) supplemented diet to increase delivery of Ca++ to the kidney and administered single daily subcutaneous injections of gentamicin, 100 mg/kg, for 10 d. Compared with a simultaneously studied group (group 1) of rats receiving identical gentamicin dosages and normal diets, Ca++ supplementation ameliorated gentamicin-induced acute renal failure. After 10 doses of gentamicin, blood-urea nitrogen values in group 1 averaged 213 +/- 15 (SE) and 25 +/- 3 (P less than 0.001) in group 2. The progressive decline in renal excretory function, as measured by BUN, in group 1 animals was accompanied by simultaneous declines in renal cortical mitochondrial function and elevations in renal cortex and mitochondrial Ca++ content, quantitative indices of the degree of renal tubular cell injury. Oral Ca++ loading markedly attenuated these gentamicin-induced derangements. After eight and 10 doses of gentamicin, mitochondria isolated from the renal cortex of group 2 rats had significantly higher rates of respiration supported by pyruvate-malate, succinate and N,N,N',N'-tetramethyl-p-phenyldiamine-ascorbate, higher rates of dinitrophenol-uncoupled respiration and greater acceptor control ratios than those measured in mitochondria isolated from the renal cortex of group 1 animals. Similarly, after 8 and 10 doses, renal cortex and renal cortical mitochondrial Ca++ content of group 2 was significantly lower than values observed in group 1. Thus, dietary calcium supplementation significantly protected against gentamicin-induced renal tubular cell injury and, consequently, gentamicin-induced acute renal failure. The mechanism for this protective effect of Ca++ may relate to the manner in which this polycationic antibiotic interacts with anionic sites, primarily the acidic phospholipids of renal membranes. In this regard, Ca++ was found to be a competitive inhibitor both of 125I-gentamicin binding to renal brush border membranes, the initial site of interaction between gentamicin and renal proximal tubule cells, with a composite inhibition constant (Ki) of 12 mM and of 125I-gentamicin binding to phosphatidic acid, an important membrane acidic phosph
已知二价阳离子Ca++和Mg++能竞争性抑制大量氨基糖苷类与膜的相互作用，因此在体外，Ca++能急性预防这些抗生素的神经毒性和耳毒性作用。由于庆大霉素诱导的血浆和亚细胞膜损伤似乎是庆大霉素肾毒性的关键致病事件，Ca++在庆大霉素诱导的急性肾衰竭中可能发挥类似的保护作用。为了在体内验证这种可能性，给大鼠（第2组）喂食补充4%钙（以CaCO3形式）的饮食，以增加Ca++向肾脏的输送，并每天皮下注射一次庆大霉素，剂量为100mg/kg，共10天。与同时研究的接受相同庆大霉素剂量和正常饮食的大鼠组（第1组）相比，补充Ca++改善了庆大霉素诱导的急性肾衰竭。在给予10剂庆大霉素后，第1组的血尿素氮值平均为213±15（SE），第2组为25±3（P<0.001）。第1组动物中，以血尿素氮衡量的肾排泄功能逐渐下降，同时伴有肾皮质线粒体功能下降以及肾皮质和线粒体Ca++含量升高，这些都是肾小管细胞损伤程度的定量指标。口服Ca++负荷显著减轻了这些庆大霉素诱导的紊乱。在给予8剂和10剂庆大霉素后，从第2组大鼠肾皮质分离的线粒体，在丙酮酸-苹果酸、琥珀酸和N,N,N',N'-四甲基-p-苯二胺-抗坏血酸支持下的呼吸速率显著更高，二硝基苯酚解偶联呼吸速率更高，受体控制率比从第1组动物肾皮质分离的线粒体中测得的更高。同样，在给予8剂和10剂后，第2组的肾皮质和肾皮质线粒体Ca++含量显著低于第1组观察到的值。因此，饮食中补充钙显著预防了庆大霉素诱导的肾小管细胞损伤，进而预防了庆大霉素诱导的急性肾衰竭。Ca++这种保护作用的机制可能与这种聚阳离子抗生素与阴离子位点（主要是肾膜的酸性磷脂）相互作用的方式有关。在这方面，发现Ca++是125I-庆大霉素与肾刷状缘膜结合的竞争性抑制剂，肾刷状缘膜是庆大霉素与肾近端小管细胞相互作用的初始位点，其复合抑制常数（Ki）为12mM，也是125I-庆大霉素与磷脂酸结合的竞争性抑制剂，磷脂酸是一种重要的膜酸性磷脂。
