Moderate prenatal ethanol exposure in the rat promotes kidney cell apoptosis,nephron deficits,and sex-specific kidney dysfunction in adult offspring

Alcohol during pregnancy can impair fetal development and result in offspring with neurodevelopmental deficits. Less is known about how low to moderate alcohol exposure can affect other organs, such as the kidney. Here, the effects of moderate ethanol exposure throughout pregnancy on kidney development were examined using a rat model. Rats were fed a liquid diet containing 6% ethanol (vol/vol) or control (0% ethanol) throughout pregnancy. Kidneys were collected at embryonic day (E) 20 or postnatal day (PN) 30 and total glomerular (nephron) number determined using unbiased stereology. Kidney function was examined in offspring at 8 and 19 months. At E20, fetuses exposed to ethanol had fewer nephrons with increased apoptosis. Alcohol exposure caused kidney dysregulation of pro- (Bax) and anti- (Bcl-2) apoptotic factors, and reduced expression of the cell proliferation marker, Ki67. Prenatal alcohol decreased expression of Gdnf and Tgfb1, important regulators of branching morphogenesis, in male fetuses. At PN30, kidney volume and nephron number were lower in offspring exposed to prenatal alcohol. Urine flow and osmolality were normal in offspring exposed to alcohol however sodium excretion tended to be lower in females prenatally exposed to alcohol. Findings suggest exposure to moderate levels of alcohol during pregnancy results in impaired kidney development and leads to a permanent nephron deficit. Although the impact on adult kidney function was relatively minor, these data highlight that even at moderate levels, alcohol consumption during pregnancy can have deleterious long-term outcomes and should be avoided.     

The distal nephron is preferentially infiltrated by inflammatory cells in acute interstitial nephritis

Summary In acute interstitial nephritis (AIN), mononuclear cells invade the tubules (tubulitis). The segmental localization of tubulitis is not precisely known. To clarify this question, formalin-fixed kidney biopsy specimens from 13 patients with AIN were studied stereologically by identifying cortical tubules with segment-specific markers. The periodic acid-Schiff reaction, peanut lectin, and antibodies against Tamm-Horsfall protein and epidermal cytokeratins all applied to the same section were used to identify the proximal tubules (PTs), distal convoluted tubules, distal straight tubules, and the cortical collecting system (connecting tubules and cortical collecting ducts), respectively. Morphometrically, an estimate of the relative volume of the inflammatory cell infiltrates within each category of tubular segments was obtained. Inflammatory cells were infrequently found in PTs (1.2%) but were frequently localized in distal tubules and the cortical collecting system (7.6%). There was no difference in the amount of the inflammatory cell infiltrate within these segments. Re-examination of an electron microscopic study of AIN carried out in this laboratory revealed that mononuclear cells were rarely seen in convoluted PTs but were frequently observed in straight PTs and all segments distal to them. The observations indicate that it is the distal nephron which is primarily affected by inflammatory cell infiltration in AIN.     

Ochratoxin A impairs “postproximal” nephron function in vivo and blocks plasma membrane anion conductance in Madin-Darby canine kidney cells in vitro

Ochratoxin A (OTA) is a widespread nephrotoxin which causes porcine nephropathy and is supposed to have caused the human Balkan endemic nephropathy. We performed experiments in vivo and in vitro to elucidate the mechanism of OTA action in renal epithelium. Application of OTA to male Wistar rats [1.25 mol/ (kg · day)] for 6 days led to a reduction of glomerular filtration rate (to 63% of control), an increased fractional water (194% of control), Na⁺ (199% of control), K⁺ (147% of control) and Cl^– (270% of control) excretion and an increased dependence of the osmole clearance on urine flow. Acute application of OTA to rats (3 mol/ kg) increased urinary pH from 6.0±0.2 to 6.6±0.1 and urinary NaCl excretion, but decreased titratable acid excretion to 47% of control. As these in vivo findings may be the result of an action of OTA beyond the proximal tubule (postproximal) we investigated the effect of OTA on cultured Madin-Darby canine kidney (MDCK) cells, regarded as a model of collecting duct epithelium. In confluent monolayers formed by MDCK cells OTA reduced the number of domes in a dose-dependent manner and impaired the formation of a transepithelial Cl^– gradient. Electrophysiological measurements in giant MDCK cells revealed that OTA blocks fractional anion conductance of the plasma membrane with an IC₅₀ value of 30±5 nmol/l, unmasking OTA as a naturally occurring anion conductance blocker about 20-times more effective than the most potent synthetic blocker 5-nitro-2-(3-phenylpropyl-amino) benzoic acid (NPPB) (IC₅₀=600±50 nmol/l). The effects of OTA and NPPB are not additive. We conclude that OTA acts acutely on postproximal parts of the nephron. This effect is probably located in the collecting duct and is due to its inhibitory action on plasma membrane anion conductance.With technical assistance of Ruth Freudinger and Sigrid Mildenberger.     

Autoregulation of superficial nephron function in the alloperfused dog kidney

Isolated dog kidneys were each pumpperfused by another dog during 4 experimental periods at perfusion pressures (PP) of 21, 17, 13, and 8 kPa, resp. (i. e. 160, 130, 95, and 60 mm Hg). At the 3 highest PP values, the total kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were perfectly autoregulated while at the lowest value both values were significantly lowered. No significant difference was observed between the single nephron GFR (SNGFR) of periods 1 and 2; in period 3 (PP=13 kPa) a lower value was observed (P<0.05). Free flow pressure in proximal convolution (FFP), stop-flow pressure (SFP), and peritubular capillary pressure (PCP) were not different in period 2 than in period 1, but were significantly lower in period 3 (P=0.02–0.05). Effective filatration pressure (EFP) was the highest in period 1, decreasing significantly with decreasing PP. Filtration pressure equilibrium was observed in period 4 at PP 8 kPa. Total blood flow resistance (R_T) fell with decreasing PP, the drop being due to a steep decline in afferent resistance (R_A). Efferent resistance (R_E) increased as PP decreased. Ultrafiltration coefficient (K_f) rose with declining PP both within and outside the autoregulatory range. The results indicate that the lower limit of autoregulation is higher in superficial nephrons than in the whole kidney.     

Low-grade renal cell carcinoma arising from the lower nephron: a case report with immunohistochemical, histochemical and ultrastructural studies

Most renal cell carcinomas (RCC) are composed of clear cells with sinusoid-like vasculatures and originate from the proximal tubule. On the other hand, collecting duct carcinoma (CDC) and chromophobe RCC are thought to originate from the lower nephron. In the present study, we present a case of unusual RCC. The patient was a 68-year-old Japanese woman who had developed general fatigue with hematuria. Computed tomography revealed a left renal tumor suggesting sarcoma. The resected tumor was located in the renal parenchyma, measuring 12 x 10 x 8 cm in size. Histologically, the tumor consisted principally of cuboidal cells forming parallel or radiating arrays, continuous with the spindle-shaped cells. Most parts of the tumor showed hemorrhagic necrosis. Immunohistochemically, tumor cells were positive for high molecular weight cytokeratins, vinculin, vimentin, CD15 and epithelial membrane antigen, and showed affinities with some kinds of lectins. N- and E-cadherins and beta-catenin were diffusely positive in tumor cells. Nuclear positivity for Ki-67 and p53 protein were approximately 2.0 and 1.7%, respectively. Considering its morphological and histochemical natures, this tumor is considered to have originated from the lower nephron, which is unique for a tumor of low-grade malignancy.     

Intra- and inter-nephron heterogeneity of gluconeogenesis in the rat: effects of chronic metabolic acidosis and potassium depletion

The intra- and inter-nephron heterogeneity of renal gluconeogenesis within rat proximal tubules and the effects of chronic metabolic acidosis and chronic potassium(K)-depletion were studied using isolated proximal tubules of rats by directly measuring glucose synthesized.The gluconeogenic activity from pyruvate and glutamine in control rats was almost limited to within the early proximal tubule (S1: 45.4±5.7 pmol/mm/60 min from pyruvate; 58.0±6.0 from glutamine). Very low, but detectable gluconeogenesis was observed in the middle portion of the proximal tubule (S2:9.9±2.2 from pyruvate; 4.8±1.1 from glutamine). The rate of glucose production in the terminal proximal tubule (S3) was negligible. Furthermore, gluconeogenesis from glutamine of superficial (SF) nephrons was significantly higher than that of juxtamedullary (JM) ones, whereas no difference was seen in gluconeogenesis from pyruvate.In acidotic and K-depleted rats, significant increase could be seen in S1 and S2, but the increase in S3 was not significant. By the serial determination in acidosis, the glucose production from both substrates was found to be the highest at the second 1 mm segment from the glomerulus, and it decreased downward along the proximal tubule. In acidosis, glucose production from both substrates in SF nephrons and that from glutamine in JM ones were elevated significantly compared with the control, but that from pyruvate in JM nephrons did not change.These results suggest that S1 of the SF nephron plays the most important role in gluconeogenesis in the control, whereas S1 of the JM nephron and S2 contribute to gluconeogenesis in acidotic and/or possibly K-depleted rats.     

Correlation between fluid reabsorption and proximal tubule ultrastructure during development of the rat kidney

Parallel functional and ultrastructural studies were performed in maturing rats in order to elucidate factors determining the development of proximal tubular fluid reabsorption. Three groups of hydropenic animals, which were 22 to 24, 28 to 32 and 40 to 45 days old, were studied. Nephron function was evaluated at the single nephron level by micropuncture technique. The ultrastructure of the developing proximal tubules was analysed by morphometric techniques following fixation of single nephrons. Kidney weight, proximal convoluted tubule length and diameter increased during postnatal development. SNGFR increased from 2.98 to 8.57 and to 20.5 nl/min in respective group of rats whereas proximal tubular fluid reabsorption Jv (a) increased from 0.15 to 0.22 and 0.34 μm³μm^_2-s ^_1. Parallel to the functional development the relative area of lateral and basal cell membrane increased, resulting in a constant relationship between net fluid reabsorption and the lateral and basal cell membrane area during the fourth postnatal week and then only a slight increase in this relation during the further development. The results suggest that net fluid transport during hydropenia is determined by the amount of available lateral and basal cell membranes where the transporting enzyme for sodium is located.     

糖尿病肾病与瘦素水平相关分析

目的探讨河南省汉族糖尿病肾病患者与血清瘦素水平是否关联。方法在河南省汉族人群选择180例糖尿病肾病患者;76例健康献血者,用放射免疫分析技术测定了血清瘦素水平。对尿素氮、血肌酐、尿微量白蛋白、糖化血红蛋白、体重指数等的临床指标进行了检测。结果河南省汉族糖尿病肾病患者血清瘦素水平与正常人群的血清瘦素水平比较无显著性差异(P>0.05)。结论瘦素在河南省汉族糖尿病肾病患者中可能不是主要致病原因。瘦素水平与体重指数呈正相关。