Functional basis for the glomerular alterations in uranyl nitrate acute renal failure

A Mitochondria-Targeted Heptamethine Indocyanine Small Molecular Chelator for Attenuating Uranium Nephrotoxicity

Radionuclide uranium has both a chemical and radioactive toxicity, leading to severe nephrotoxicity as it predominantly deposits itself in the kidneys after entering into human bodies. It crosses renal cell membranes, accumulates in mitochondria and causes mitochondrial oxidative damage and dysfunction. In this study, a mitochondria-targeted heptamethine indocyanine small molecule chelator modified with gallic acid (IR-82) is synthesized for uranium detoxication. Both gallic acid and sulfonic acid, as two hydrophilic endings, make IR-82, being excreted feasibly through kidneys. Gallic acid with polyphenol groups has a steady metal chelation effect and potent antioxidant ability, which may facilitate IR-82-alleviated uranium nephrotoxicity simultaneously by enhancing uranium decorporation from the kidneys and reducing mitochondrial oxidative damage. Cell viability assays demonstrate that IR-82 can significantly improve the cell viability of uranium-exposed human renal (HK-2) cells. It is also demonstrated to accumulate in mitochondria and reduce mitochondrial ROS and total intracellular ROS, as well as intracellular uranium content. In vivo imaging experiments in mice show that IR-82 could be excreted out through kidneys. ICP-MS tests further reveal that IR-82 can efficiently decrease the uranium deposition in mouse kidneys. IR-82 treatment improves the animal survival rate and renal function of experimental mice after high-dose uranium exposure. Collectively, our study may evidence that the development of uranium decorporation agents with kidney-mitochondrion dual targeting abilities is a promising strategy for attenuating uranium-induced nephrotoxicity.

Boosting Simultaneous Uranium Decorporation and Reactive Oxygen Species Scavenging Efficiency by Lacunary Polyoxometalates

The chemical toxicity and the oxidative stress induced by the internal exposure of uranium is responsible for the long-term adverse effect of in vivo contamination of uranium. An agent with simultaneous removal capability of uranium and excess reactive oxygen species (ROS) is highly desired. Herein, the lacunary Keggin-type polyoxometalate (POM) is demonstrated to selectively bind with uranyl ions in the presence of excess essential divalent ions and exhibits a compelling ROS scavenging efficiency of 78.8%. In vivo uranium decorporation assays illustrate the uranium sequestration efficiencies of 74.0%, 49.4%, and 37.1% from kidneys by prophylactic, prompt, and delayed administration of lacunary POM solution, respectively. The superior ROS quenching and uranium removal performance in comparison with all reported bifunctional agents endow lacunary polyoxometalates as novel agents to effectively protect people from injuries caused by the internal exposure of actinides.

Hinokitiol, an Advanced Bidentate Ligand for Uranyl Decorporation

Despite the critical role actinide decorporation agents play in the emergency treatment of people in nuclear accidents and other scenarios that may cause internal contamination of actinides, new ligands have seldom been reported in recent decades because the current inventory has been limited to only a handful of functional groups. Therefore, new functional groups are always being urgently sought for the introduction of advanced actinide decorporation agents. Herein, a tropolone derivative, 2-hydroxy-6-(propan-2-yl)cyclohepta-2,4,6-trien-1-one (Hinokitiol or Hino), is proposed to be a promising candidate for this purpose by virtue of its well-demonstrated high membrane permeability and high affinity for metal ions. The coordination stoichiometry of Hino with uranyl is demonstrated to be 3:1 both in an aqueous solution (pH 7.4) and in the solid state. The results of a liquid-liquid extraction experiment further show that Hino exhibits strong chelating ability and selectivity toward uranyl over biological essential metal ions (i.e., Mn²⁺, Zn²⁺, Co²⁺, and Ni²⁺) with an extraction efficiency of >90.0%. The in vivo uranyl removal efficacies of Hino in kidneys and bone of mice are demonstrated to be 67.0% and 32.3%, respectively. On the basis of the observations described above, it is highly possible that further modification of Hino will lead to a large family of multidentate agents with enhanced uranyl decorporation ability.

Hydrogeochemical Processes Governing Uranium Mobility: Inferences from the Anthropogenically Disturbed, Semi-arid Region of India

Khetri Copper Belt, Rajasthan, is anthropogenically active and geologically belongs to the Delhi super-group. A study was designed to understand the geochemical processes controlling the elemental mobility in the groundwater. Sampling sites were divided into three zones, i.e. copper, quartzite and granite mine zones depending on the type of mineral excavated. A total of 32 representative groundwater samples were collected and analysed for heavy metals and radionuclide (U) using ICP-MS. A maximum U concentration (average 87 µgL^-1) is observed in the quartzite mine zone, and minimum (average 13 µgL^-1) is found in the copper mine zone samples. A high concentration of U (maximum of 430 µgL^-1) in groundwater is attributed to mineral dissolution due to geogenic and anthropogenic activities. Despite the presence of Jaspura and Gothra granitoid in the copper mine zone, the abundance of U is low suggesting the scavenging of U by sulphides or iron oxides. Additionally, at the confluence of two geological groups, Fe concentration is found high with a low concentration of U which further confirms scavenging of U. It is evident from the results that in the absence of iron-bearing sulphides, U concentration in groundwater would be very high compared to the current concentration. It also indicates low concentration of U in the copper mine zone is due to dissolution of Fe sulphide-rich waste. The present study recommends further research to understand the feasibility of mining waste for the removal of U contamination from groundwater.

Dose estimation of radioactivity in groundwater of Srinagar City, Northwest Himalaya, employing fluorimetric and scintillation techniques

The research is a maiden study aimed to assess the radioactivity in groundwater of Srinagar City using uranium and radon as proxies. In this study, 60 water samples were collected from various water sources that include bore wells, hand pumps and lakes of Srinagar City. Among them, 45 samples were taken from groundwater with depths ranging from 6 to - 126 m and the rest of the 15 samples were collected from surface sources like lakes, rivers and tap water. A gamma radiation survey of the area was carried out prior to collection of water samples, using a gamma radiation detector. A scintillation-based detector was utilized to measure radon, while as LED fluorimetry was employed to assess uranium in water samples. The average uranium concentration was found to be 2.63 μg L^-1 with a maximum value of 15.28 μg L^-1 which is less than the globally accepted permissible level of 30 µg L^-1. ²²²Radon concentration varied from 0.2 to 38.5 Bq L^-1 with an average value of 8.9 Bq L^-1. The radon concentration in 19 groundwater samples (32% of total sites) exceeded the permissible limits of 11 Bq L^-1 set by USEPA. This information could be of vital importance to health professionals in Kashmir who are researching on the incidence of lung cancers in the region given the fact that radon is the second leading cause of lung cancers after smoking worldwide.

Melanin nanoparticles as an actinide in vivo sequestration agent with radiation protection effect

PEG grafted melanin nanoparticles exhibit codecorporation effect of U and Th as well as good ROS scavenging ability.

A 3,2-Hydroxypyridinone-based Decorporation Agent that Removes Uranium from Bones In Vivo

Searching for actinide decorporation agents with advantages of high decorporation efficiency, minimal biological toxicity, and high oral efficiency is crucial for nuclear safety and the sustainable development of nuclear energy. Removing actinides deposited in bones after intake is one of the most significant challenges remaining in this field because of the instantaneous formation of highly stable actinide phosphate complexes upon contact with hydroxyapatite. Here we report a hydroxypyridinone-based ligand (5LIO-1-Cm-3,2-HOPO) exhibiting stronger affinity for U(VI) compared with the reported tetradentate hydroxypyridinone ligands. This is further revealed by the first principles calculation analysis on bonding between the ligand and uranium. Both in vitro uranium removal assay and in vivo decorporation experiments with mice show that 5LIO-1-Cm-3,2-HOPO can remove uranium from kidneys and bones with high efficiencies, while the decorporation efficiency is nearly independent of the treatment time. Moreover, this ligand shows a high oral decorporation efficiency, making it attractive for practical applications.

Uranium distribution in groundwater and assessment of age dependent radiation dose in Amritsar, Gurdaspur and Pathankot districts of Punjab, India

A comprehensive study of seasonal variation of uranium distribution in groundwater of Amritsar, Gurdaspur and Pathankot districts of Punjab, India and assessment of associated radiological risks, chemical risks and effective radiation dose for different age groups, was conducted to determine its health impact on humans residing in these regions. Physicochemical parameters such as pH, EC, TDS, total hardness and contents of various anions such as carbonates/bicarbonates, chlorides, fluorides, nitrates, sulphates and phosphates in groundwater were also analysed to determine correlation between groundwater chemistry and uranium distribution. The average values of uranium concentration in ground water samples of Amritsar, Gurdaspur and Pathankot districts were found to be 8.6 μg L^-1, 4.3 μg L^-1 and 3.0 μg L^-1, respectively, in pre-monsoon and 8.8 μg L^-1, 4.9 μg L^-1 and 3.4 μg L^-1, respectively, in post-monsoon. The uranium concentration in majority of the ground water samples was found to be below the permissible limit of 30 μg L^-1 recommended by World Health Organization (WHO, 2011). In all three districts, TDS, EC and bicarbonates were found to have positive correlation with observed uranium contents in both seasons. The annual effective dose due to ingestion of uranium through drinking water was found to be less than the prescribed limit of 100 μSv y^-1 given by WHO (2004). Radiological and chemical toxicity risk assessment of uranium in groundwater was also carried out and found to be within the permissible values of 1.67 × 10^-4 and 4.53 μg kg^-1 day^-1 respectively, recommended by Atomic Energy Regulatory Board (AERB, 2004).

3,2-Hydroxypyridinone-Grafted Chitosan Oligosaccharide Nanoparticles as Efficient Decorporation Agents for Simultaneous Removal of Uranium and Radiation-Induced Reactive Oxygen Species in Vivo

Most of the key radionuclides in the nuclear fuel cycle, such as actinides, possess a combination of heavy metal chemotoxicity and radiotoxicity and therefore represent a severe threat to the ecological environment and public safety. The radiotoxicity originates from direct radiation-induced organ damage and indirect damage, mostly through radiation-induced reactive oxygen species (ROS). Although effective chelating agents that can accelerate the excretion of actinides, such as uranium, have been developed in the past several decades, very few of them can reduce radiation-induced damage from internal contamination. In fact, the strategy of simultaneous removal of actinides and their induced-ROS in vivo has scarcely been considered. Here, we report a 3,2-hydroxypyridinone-grafted chitosan oligosaccharide nanoparticle (COS-HOPO) as a new type of decorporation agent that is effective for the removal of both uranium and ROS in vivo. The cytotoxicity and decorporation assays indicate that the marriage of chitosan oligosaccharide (COS) and hydroxypyridinone (HOPO) gives rise to a remarkable decrease in toxicity and promotion of the uranium removal capability from both kidneys and femurs. The decorporation efficacy can reach up to 43% in rat proximal tubular epithelial cells (NRK-52E), 44% in kidneys, and 32% in femurs. Moreover, the ROS levels of the cells treated with COS-HOPO are significantly lower than those of the control group, implying a promising radiation protection effect. The detoxification mechanism of COS-HOPO is closely related to both chelating U(VI)- and scavenging U(VI)-induced intracellular ROS.

Efficacy of Chelator CBMIDA-CaNa2 for the Removal of Uranium and Protection against Uranium-induced Cell Damage in Human Renal Proximal Tubular Cells

In animal experiments, catechol-3,6-bis(methyleiminodiacetic acid) (CBMIDA) was proven to be an effective chelator for the decorporation of uranium (U)(VI). In the present study, the authors investigated the molecular processes of CBMIDA-CaNa2 on the removal of U(VI) at the cellular level and explored its protective effects and mechanism against U(VI)-induced cell damage in HK-2 human renal proximal tubular cells. The results indicated that the chelating U(VI) effect of CBMIDA-CaNa2 was superior compared to that of DTPA-CaNa3; more specifically, at concentrations of 50 and 250 μM, CBMIDA-CaNa2 can significantly reduce U(VI) uptake and increase U(VI) release in U(VI)-exposed HK-2 cells after immediate or 24-h and 48-h delayed chelator administration better than those of DTPA-CaNa3. Furthermore, CBMIDA-CaNa2 significantly decreased the lactate dehydrogenase release and the formation of micronuclei and inhibited the production of intracellular reactive oxygen species (ROS) in HK-2 cells exposed to U(VI), whereas DTPA-CaNa3 was demonstrated to be ineffective. By reviewing the results of animal experiments conducted by several other investigators, including this lab, the authors found that removal efficacy and protective effects of these two chelators for U(VI) at the cellular level agreed well with those of animal studies. In addition, although U(VI) induced the increase of metallothionein protein expression in HK-2 cells, CBMIDA-CaNa2 can mobilize and remove the U(VI) from metallothionen (MT) after 48-h delayed chelator treatment. These results suggested that CBMIDA-CaNa2 protected against U(VI)-induced HK-2 cells damaged by reducing U(VI) uptake, increasing U(VI) release and scavenging the U(VI)-induced intracellular ROS.

Chronic Exposure to Uranium Leads to Iron Accumulation in Rat Kidney Cells

After it is incorporated into the body, uranium accumulates in bone and kidney and is a nephrotoxin. Although acute or short-term uranium exposures are well documented, there is a lack of information about the effects of chronic exposure to low levels of uranium on both occupationally exposed people and the general public. The objective of this study was to identify the distribution and chemical form of uranium in kidneys of rats chronically exposed to uranium in drinking water (40 mg uranium liter(-1)). Rats were killed humanely 6, 9, 12 and 18 months after the beginning of exposure. Kidneys were dissected out and prepared for optical and electron microscope analysis and energy dispersive X-ray (XEDS) or electron energy loss spectrometry (EELS). Microscopic analysis showed that proximal tubule cells from contaminated rats had increased numbers of vesicles containing dense granular inclusions. These inclusions were composed of clusters of small granules and increased in number with the exposure duration. Using XEDS and EELS, these characteristic granules were identified as iron oxides. Uranium was found to be present as a trace element but was never associated with the iron granules. These results suggested that the mechanisms of iron homeostasis in kidney could be affected by chronic uranium exposure.

Renal hemodynamics in rats with cadmium-induced nephropathy

Glomerular filtration rate (GFR) is known to decline in patients with cadmium (Cd)-induced nephropathy. However renal hemodynamics in Cd-induced nephropathy remain unknown. We investigated renal hemodynamics in experimental Cd-induced nephropathy. Male Sprague-Dawley rats were given 0.18 mg/rat of cadmium chloride i.p. three times a week for 3 and 16 months. Age-matched control rats were given physiological saline. Mean arterial pressures after 3 and 16 months were identical among the groups. In comparison with age-matched control rats, significant decreases in GFR associated with a significantly lower filtration fraction (FF) were demonstrated in both groups of Cd-treated rats, but the changes were more prominent in the 16-month Cd-treated rats. Renal plasma flow was significantly decreased in the 3-month Cd-treated rats whereas it was preserved in the 16-month Cd-treated rats because of anemia. Urinary sodium excretions in both groups of Cd-treated rats were significantly greater than those in the respective control rats. On light microscopic examination, only mild degeneration of tubular cells and interstitial edema in limited areas of the proximal tubules were observed in the 3-month Cd-treated rats. In the 16-month Cd-treated rats multifocal tubular atrophy and interstitial fibrosis in the outer cortex were noted. Electron microscopic examinations revealed conspicuous degenerative changes in the proximal tubular epithelial cells, diffuse thickening of glomerular basement membranes, and foot process fusions in 16-month Cd-treated rats. These data suggested that the decline in GFR in the Cd-treated rats resulted mainly from the decline in FF, which might be functional rather than structural in origin and might be associated with proximal tubular dysfunctions.

Uranyl nitrate-induced proximal tubule alterations in rabbits: a quantitative analysis

Naturally occurring uranium in drinking water is a significant health concern in several areas of North America. Because the kidney is a known target organ to examine the effects of uranium or its compounds, the objective of this study was to determine whether kidney repair occurs after exposure to, and withdrawal of, uranyl nitrate (UN). This work, part of a larger study to establish safe levels of uranium in drinking water supplies, examined the ultrastructural changes in proximal tubule cells of New Zealand white rabbits following subchronic exposure to UN in water and for 91 days after exposure ended. The rabbit was chosen as the experimental animal because of its high sensitivity to uranium. Animals were exposed to 24 or 600 mg UN per liter (UN/L) in drinking water for 91 days, with no recovery or recovery periods of 45 or 91 days. Ultrastructural changes, quantified by a stereological image analysis system based on point counting, were observed in renal proximal tubules (PTs). Each electron micrograph was statistically considered an experimental unit. The severity of lesions was directly proportional to the dose. Animals exposed to 600 mg UN/L had the most severe lesions; nevertheless, alterations were remarkable in animals exposed to the low dose. At both recovery periods, the lesions were significantly more severe than those in animals of the no-recovery group, which may result from the kidney's ability to store uranium. The PT cells had increased lysosomal and vacuolar mass as well as variations in mitochondrial mass. In addition, there was epithelial cell degeneration with a focal loss of brush borders, thickening and splitting of tubular basement membrane, and occasionally cell necrosis. Interstitial fibrosis of the renal cortex persisted as the recovery period increased in the animals of UN-dosed groups. Alterations may be due to disturbed fluid transport across the PT and other cells and decreased cell respiration resulting from damaged cell constituents. Cell damage caused by UN in drinking water persisted throughout the 91-day recovery period. By eventually determining the no observable effect level for the kidney by UN, this study may assist in devising a model to ascertain the safe levels of uranium in water.

Comparative effects of the chelators sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron) and diethylenetriaminepentaacetic acid (DTPA) on acute uranium nephrotoxicity in rats

Sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron) and diethylenetriaminepentaacetic acid (DTPA) are two chelating agents that have been demonstrated to be effective in the treatment of experimental poisoning by a number of heavy metals. In this study, the effects of Tiron and DTPA on uranium-induced nephrotoxicity were evaluated in a rat model. A series of four Tiron or DTPA injections was administered intraperitoneally to adult male Sprague-Dawley rats immediately after a single subcutaneous injection of uranyl acetate dihydrate (5 mg/kg) and at 24, 48 and 72 h thereafter. Positive and negative control groups received 0.9% saline with or without uranyl acetate, respectively. Tiron effectiveness was assessed at 400, 800 and 1600 mg/kg, whereas DTPA was administered at 250, 500 and 1000 mg/kg. Although the urinary excretion of uranium was significantly enhanced by Tiron administration, significant amounts of uranium still remained in the kidney at the end of the treatment. However, the partial reduction of the renal uranium concentrations was in accordance with the amelioration noted in some urinary and serum indicators of uranium nephrotoxicity. Moreover, Tiron administration also reduced the severity of the uranium-induced histological alterations in the kidney. According to these results, Tiron offers only a modest encouragement with regard to its possible therapeutic potential to treat acute uranium-induced nephrotoxic effects. In turn, DTPA was less effective than Tiron in protecting against the nephrotoxicity of uranium in rats.

Effects of oxygen free radical scavengers on uranium-induced acute renal failure in rats

Study was made to determine whether oxygen free radicals mediate uranium-induced acute renal failure (ARF). Superoxide dismutase (SOD), a superoxide anion scavenger, did not prevent uranium acetate (UA) (5 mg/kg, i.v.)-induced renal injury 48 h after injection. In contrast, dimethylthiourea (DMTU), a hydroxyl radical scavenger, significantly attenuated UA-induced rise in serum creatinine concentration (1.11 +/- 0.05 (DMTU) vs. 1.40 +/- 0.06 mg/dl (control), p < .05), and tubular necrosis. Dimethyl sulfoxide (DMSO), a hydroxyl radical scavenger, decreased UA-induced tubular damage. UA injection caused no increase in renal cortical malondialdehyde (MDA) content. DMTU and DMSO did not modify intrarenal MDA content. UA administration brought about significant increase in plasma renin activity but not in renal cortical renin content. Treatment with DMTU and DMSO had no effect on plasma renin activity or intrarenal renin content. It follows from these findings that DMTU and DMSO may attenuate UA-induced renal injury. Such a protective effect would not be mediated through modulation of lipid peroxidation or renin activity.

Physiologic adaptations of the tubuloglomerular feedback system

Knowledge of the existence of a tubuloglomerular feedback system has been available for many years. Only recently, however, have tenable hypotheses and supporting experimental data become available which have served to provide details regarding the complex inner workings of this system. The facility for examining this integrated physiologic network has derived, in large part, from the routine ability to perform in vivo micropuncture. We anticipate that further advances in this field will hinge on the development of additional experimental techniques to allow cellular biologic aspects of the system to be closely monitored in situ.

A single nephron model of acute tubular injury: role of tubuloglomerular feedback

A single nephron model of nephrotoxic tubular injury was established to examine the mechanism whereby acute tubular damage contributes to reductions in nephron filtration rate (SNGFR). Acute microperfusion of 0.5 ng of uranyl nitrate (UN) into the early proximal tubule produced a significant reduction (16 to 30%) in SNGFR measured in both distal and proximal tubules of the same nephron and a decrease in absolute proximal reabsorption. Microperfused inulin was retained in the tubule suggesting this finding reflected a true reduction in SNGFR. Concurrent infusion of high dose furosemide (2 x 10(-4)M) and bumetanide (2 x 10(-5) M), but not low dose furosemide (2 x 10(-5) M), prevented the UN induced reduction in SNGFR. High dose furosemide begun after UN perfusion also prevented reduction in SNGFR. Continuous direct measurement of glomerular capillary hydrostatic pressure revealed no change. Distal intratubular Na+ and Cl- concentration increased significantly after UN perfusion. Activation of tubuloglomerular feedback mechanisms best explains the reduction in glomerular ultrafiltration that is characteristic of nephrotoxic forms of tubular injury.

Early effects of uranyl nitrate on respiration and K+ transport in rabbit proximal tubule

The mechanisms by which uranyl nitrate (UN) is toxic to the proximal tubule are incompletely understood. To define these further we studied potassium (K+) transport and oxygen consumption (QO2) in rabbit proximal tubule suspensions in vitro immediately after exposure to UN using extracellular O2- and K+-sensitive electrodes. UN caused a cumulative dose-dependent inhibition of proximal tubule QO2, with a threshold concentration of 5 x 10(-5) M. Kinetic analysis suggested two patterns of cell injury: a higher affinity inhibition of QO2 with a Ki of 5 x 10(-4) M, and a lower affinity inhibition of QO2 with a Ki of 10 mM. QO2 was studied in detail in the presence of these Ki concentrations of UN to define the initial cellular events. The results indicated that different cellular processes displayed different sensitivities to UN. At submillimolar concentrations UN caused progressive selective inhibition of ouabain-insensitive QO2 (15% inhibition at 2 minutes). Ouabain-sensitive QO2 and nystatin-stimulated QO2 were not affected, suggesting that Na+,K+-ATPase activity and its coupling to mitochondrial ATP synthesis were intact. Direct measurement of proximal tubule net K+ flux confirmed that Na+,K+-ATPase activity was unchanged. Similarly, UN did not inhibit basal (state 4) or ADP-stimulated (state 3) mitochondrial QO2 in digitonin-permeabilized tubules, confirming that the mitochondria were intact. In contrast, higher concentrations of UN (greater than or equal to 1 mM) caused rapid inhibition of QO2 and net K+ efflux, due to inhibition of Na+,K+-ATPase activity and mitochondrial injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Phlorizin-induced glycosuria does not prevent gentamicin nephrotoxicity in rats

Because rats with streptozotocin-induced diabetes mellitus (DM) have a high solute diuresis (glycosuria of 10 to 12 g/day), we have suggested that this may in part be responsible for their resistance to gentamicin-induced acute renal failure (ARF). The protection from gentamicin nephrotoxicity was studied in non-diabetic rats with chronic solute diuresis induced by blockage of tubular glucose reabsorption with phlorizin (P). DM rats with mild glycosuria (similar in degree to that of the P treated animals) were also studied. Unanesthetized adult female, Sprague-Dawley rats were divided in four groups and studied for 15 days. Group 1 (P alone) received P, 360 mg/day, for 15 days; Group II (P + gentamicin); Group III (gentamicin alone) and Group IV (mild DM + gentamicin). Nephrotoxic doses (40 mg/kg body wt/day) of gentamicin were injected during the last nine days of study to the animals of groups II to IV. In Group I, P induced a moderate and stable glycosuria (3.9 +/- 0.1 g/day, SE), and no functional or morphologic evidence of renal dysfunction (baseline CCr 2.1 +/- 0.1 ml/min, undetectable lysozymuria) or damage (tubular necrosis score [maximum 4], zero). In Group II, P did not prevent gentamicin-ARF (maximal decrease in CCr at day 9.89%, P less than 0.001; peak lysozymuria, 1863 +/- 321 micrograms/day; and tubular necrosis score, 3.9 +/- 0.1). These values were not different from those of Group III: maximal decrease in CCr 73% (P less than 0.001); lysozymuria, 2147 +/- 701 micrograms/day; tubular necrosis score, 3.8 +/- 0.1.(ABSTRACT TRUNCATED AT 250 WORDS)

Gentamicin-induced glomerulotoxicity in the pregnant rat

Ten daily injections of gentamicin, 40 mg/kg/d intraperitoneal (IP), produced a marked reduction in the glomerular capillary ultrafiltration coefficient (Kf) of virgin female Munich-Wistar rats without eliciting significant reductions in glomerular filtration rate (GFR) or single nephron (SN)GFR. A similar gentamicin-induced decrease in Kf was seen in midterm pregnant (day 12) rats and the normal gestational increase in GFR and SNGFR was blunted by gentamicin. Concomitant converting enzyme inhibition (CEI) (MK 421, 50 mg/L drinking water) completely prevented the gentamicin-induced decrease in Kf in virgin females, thus confirming that the gentamicin-induced decline in Kf is mediated by angiotensin II (ANG II). These studies indicate that pregnancy neither exacerbates nor ameliorates gentamicin-induced glomerulotoxicity and also that glomerular ANG II responsivity is not diminished in midterm pregnant rats.

The effect of saline loading on uranium-induced acute renal failure in rats

Studies were performed to examine the effect of saline loading on uranium-induced acute renal failure (ARF) in rats. Forty-eight hours after the i.v. injection of uranyl acetate (UA, 5 mg/kg), inulin clearance rate (Cin) decreased to approximately 43% of the control value in water drinking rats (P less than 0.005). Animals receiving continuous isotonic saline infusion following UA showed higher urine flow and Cin (60% of control, P less than 0.01), and lessened intratubular cast formation when compared with water-drinking ARF rats. A short-term saline infusion following UA did not attenuate the decline in Cin (43% of control). An inverse relationship was found between Cin and the number of casts (r = -0.75, P less than 0.01). Multiple regression analysis showed that standardized partial regression coefficient is statistically significant between Cin and cast formation (-0.69, P less than 0.05), but not between Cin and tubular necrosis (-0.07, P greater than 0.05). Renin depletion caused by DOCA plus saline drinking did not attenuate the decline in Cin in ARF (47% of control). No significant difference was found in urinary uranium excretion between water-drinking and saline-infused ARF rats. The findings suggest that continuous saline infusion following UA attenuates the decline in Cin in ARF rats; and that this beneficial effect of saline loading is associated with lessened cast formation rather than with suppressed renin-angiotensin activity or enhanced urinary-uranium excretion.

Glomerular hemodynamics in mercury-induced acute renal failure

As manifest by tubular collapse and the virtual absence of flow into the glomerulotubular junction (GTJ), filtration in most nephrons (SNGFR) of rats poisoned with 9 mg/kg body wt HgCl2 16 to 28 hours earlier was virtually absent. Arterial colloid osmotic pressure (COPA) and Bowman's space pressure (PBS) were modestly depressed (P less than 0.05 or below), and mean blood pressure was reduced from 115 +/- 2 mm Hg (SEM) to 97 +/- 1 mm Hg (P less than 0.001). Glomerular capillary hydraulic pressure (Pg), 25.6 +/- 1.3 mm Hg was some 24 mm Hg lower than control (P less than 0.001) and yielded a net afferent effective filtration pressure (Pnet) of 4.1 +/- 1.2 mm Hg. Excluding three rats with values greater than 10 mm Hg, Pnet averaged 2.0 +/- 0.9 mm Hg (N = 17 rats) versus 20.0 +/- 1.8 mm Hg in controls (N = 10, P less than 0.001), the former being statistically almost indistinguishable from 0 mm Hg and barely able to support any filtration. This decrease in Pg was caused by a major increase in preglomerular resistance (RA) and a reciprocal fall in efferent arteriolar resistance (RE), the RA/RE ratio of 7.2 +/- 0.8 being fourfold higher than control (P less than 0.001). Renocortical blood flow was not different from control (P greater than 0.2). A wide spread of Pg values in individual glomeruli and the absence of tubular flow despite the appearance of i.v. injected lissamine green in a quadrant of surface glomeruli suggested the possibility of a greatly increased, glomerular capillary resistance. It is concluded that reciprocal changes in RA and RE are the immediate cause of filtration failure in this form of ARF and that, in the virtual absence of filtration, tubular leakage can play no important role. Since PBS was depressed in both the developmental and established phases of ARF, tubular obstruction appears to play no direct role in the pathogenesis of this particular model of murine acute renal failure.

Acute renal failure: the glomerular and tubular connection

Acute renal failure (ARF) is a common clinical entity which results from multiple causes. Experimental models in animals have duplicated many of the clinical syndromes which can be classified into (1) ARF due to increased filtered load of endogenous and exogenous materials, (2) ARF associated with exogenous nephrotoxins and (3) ischemic forms of renal failure secondary to hypoperfusion and hypotension. The mechanisms leading to the reduction in GFR are multiple and the alterations in determinants of nephron filtration rate and degree of tubular backleak and obstruction are described for each of these subtypes of experimental ARF. The specific mechanisms whereby tubular damage translates into a reduction in GFR in ARF are discussed for each subtype of ARF. Tubular damage can often be dissociated from the reduction in GFR, possibly by inhibiting tubuloglomerular feedback responses, but such increases in GFR and nephron filtration rate are not necessarily beneficial to the organism because of potential volume depletion and the risk of magnifying further tubular damage. Information on the physiologic role of tubuloglomerular feedback activity in ARF is provided and supports the concept that feedback induced reductions in GFR after tubular injury may preserve extracellular volume and minimize further tubular damage. Reductions in tubular metabolic work appears to prevent and ameliorate further tubular injury after the initial insult. The mechanisms which associate changes in GFR and tubular damage can now be described, and therapies which improve GFR without correcting the tubular damage may compound the clinical problem and increase renal damage.