Wedeen R P, Levendoglu-Tugal O, Batuman V, Cheeks C
Proc Soc Exp Biol Med. 1984 Oct;177(1):120-5. doi: 10.3181/00379727-177-41920.
Tubular transport of oxalate is thought to be an energy-mediated process which may contribute to the renal deposition of calcium oxalate in a variety of pathologic states. In order to examine this possibility, the renal handling of oxalate was investigated in rat renal cortical slices in vitro. Slices incubated in vitro with 1 microM [14C]oxalate in Krebs-Ringer bicarbonate buffer at 25 degrees C for 180 min achieved a mean slice to medium ratio of 2.8 +/- 0.08 (SEM) and a mean tissue concentration of 7.7 +/- 0.2 mumol/kg dry wt (N = 64). Section freeze-dry autoradiographs demonstrated maximum uptake within proximal tubule cells but no crystals were evident. Substituting N2 for O2, adding KCN, or removing Ca2+ increased uptake of 14C-oxalate. Dinitrophenol (DNP) and iodoacetamide (IoAc), however, significantly decreased, and O degrees C eliminated slice uptake. Slices incubated with 100 microM [14C]oxalate showed a further increase in tissue accumulation and the appearance of [14C]oxalate crystals. Crystals formed in vitro were deposited throughout the tissue. Oxalic acid did not appear to share the organic acid by renal cortical slices in vitro is largely independent of energy-mediated mechanisms.
草酸盐的肾小管转运被认为是一个能量介导的过程，在多种病理状态下可能导致草酸钙在肾脏沉积。为了检验这种可能性，对大鼠肾皮质切片进行体外研究，以观察肾脏对草酸盐的处理情况。切片在含有1微摩尔[¹⁴C]草酸盐的Krebs-Ringer碳酸氢盐缓冲液中于25℃体外孵育180分钟，切片与培养基的平均比值达到2.8±0.08（标准误），组织平均浓度为7.7±0.2微摩尔/千克干重（N = 64）。切片冷冻干燥放射自显影片显示近端小管细胞内摄取量最大，但未见晶体。用氮气代替氧气、添加氰化钾或去除钙离子可增加¹⁴C-草酸盐的摄取。然而，二硝基苯酚（DNP）和碘乙酰胺（IoAc）显著降低摄取量，0℃时切片摄取量消失。用100微摩尔[¹⁴C]草酸盐孵育的切片显示组织蓄积进一步增加，且出现[¹⁴C]草酸盐晶体。体外形成的晶体沉积于整个组织。草酸似乎不与其他有机酸共享转运机制，肾皮质切片在体外对草酸的摄取很大程度上独立于能量介导机制。
