Gilbert R M, Weber H, Turchin L, Fine L G, Bourgoignie J J, Bricker N S
J Clin Invest. 1976 Dec;58(6):1348-57. doi: 10.1172/JCI108590.
The concentrating ability of the kidney was studied by clearance and micropuncture techniques and tissue slice analyses in normal rats with two intact kidneys (intact controls), normal rats with a solitary kidney (uninephrectomized controls), and uremic rats with a single pyelonephritic kidney. Urinary osmolality after water deprivation for 24 h and administration of antidiuretic hormone was 2,501+/-217 and 2,874+/-392 mosmol/kg H2O in intact and uninephrectomized control rats, respectively, and 929+/-130 mosmol/kg H2O in pyelonephritic rats (P less than 0.001 compared to each control group). Fractional water reabsorption and concentrating ability were significantly decreased in the pyelonephritic group, and, to achieve an equivalent fractional excretion of urea, a greater fractional excretion of water was required in the pyelonephritic rats than in the control rats. Whole animal glomerular filtration rate was 1.57+/-0.19 ml/min and 1.39+/-0.18 ml/min in intact and in uninephrectomized controls, respectively, and 0.30+/-0.07 ml/min in pyelonephritic rats (P less than 0.001 compared to each control group). Single nephron glomerular filtration rate was 35.6+/-3.8 nl/min in intact control rats and was significantly increased (P less than 0.05) in both uninephrectomized (88.0+/-10.8 nl/min) and pyelonephritic rats (71.5+/-14.4 nl/min). In all groups fractional water delivery and fractional sodium delivery were closely comparable at the end of the proximal convoluted tubule and at the beginning of the distal convoluted tubule. In contrast, fractional urea delivery out of the proximal tubule was greater in the intact control group (73+/-8%) than in either the uninephrectomized (52+/-2%) or the pyelonephritic group (53+/-3%) (P less than 0.005). Fractional urea delivery at the early part of the distal tubule increased significantly to 137+/-11% and 93+/-6% of the filtered load in intact control and uninephrectomized control rats, respectively (P less than 0.001 compared to the late proximal values of each group), but failed to increase significantly in pyelonephritic rats (65+/-13%), indicating interruption of the normal recycling of urea in the latter group. Analysis of tissue slices demonstrated a rising corticopapillary gradient for total tissue water solute concentration as well as for tissue water urea concentration in both groups of control rats. In contrast, the pyelonephritic animals exhibited no similar gradients from cortex to papilla. These data indicate that the pyelonephritic kidney fails to recycle urea and accumulate interstitial solute. The latter must inevitably lead to a concentrating defect.
通过清除率、微穿刺技术和组织切片分析，研究了双侧肾脏完整的正常大鼠（完整对照组）、单肾大鼠（单侧肾切除对照组）和患有单侧肾盂肾炎的尿毒症大鼠的肾脏浓缩能力。禁水24小时并注射抗利尿激素后，完整对照组和单侧肾切除对照组大鼠的尿渗透压分别为2501±217和2874±392 mosmol/kg H₂O，而肾盂肾炎大鼠的尿渗透压为929±130 mosmol/kg H₂O（与各对照组相比，P＜0.001）。肾盂肾炎组的水重吸收分数和浓缩能力显著降低，并且为了实现等量的尿素排泄分数，肾盂肾炎大鼠比对照大鼠需要更大的水排泄分数。完整对照组和单侧肾切除对照组大鼠的全动物肾小球滤过率分别为1.57±0.19 ml/min和1.39±0.18 ml/min，而肾盂肾炎大鼠的肾小球滤过率为0.30±0.07 ml/min（与各对照组相比，P＜0.001）。完整对照组大鼠的单肾单位肾小球滤过率为35.6±3.8 nl/min，单侧肾切除大鼠（88.0±10.8 nl/min）和肾盂肾炎大鼠（71.5±14.4 nl/min）的单肾单位肾小球滤过率均显著升高（P＜0.05）。在所有组中，近端曲管末端和远端曲管起始处的水输送分数和钠输送分数密切可比。相反，完整对照组近端小管的尿素输送分数（73±8%）高于单侧肾切除组（52±2%）或肾盂肾炎组（53±3%）（P＜0.005）。在完整对照组和单侧肾切除对照组大鼠中，远端小管早期的尿素输送分数分别显著增加至滤过负荷的137±11%和93±6%（与每组近端小管晚期的值相比，P＜0.001），但在肾盂肾炎大鼠中未显著增加（65±13%），这表明后一组中尿素的正常再循环中断。组织切片分析表明，两组对照大鼠的皮质-乳头体总组织水溶质浓度梯度以及组织水尿素浓度梯度均升高。相反，肾盂肾炎动物从皮质到乳头体未表现出类似的梯度。这些数据表明，肾盂肾炎肾脏无法再循环尿素并积累间质溶质。后者必然会导致浓缩功能缺陷。
