Dietary control of the renal absorption and excretion of alpha 2u-globulin

Streptozotocin induces alpha-2u globulin nephropathy in male rats during diabetic kidney disease

BACKGROUND

Alpha-2u globulin nephropathy mainly shows toxicological pathology only in male rats induced by certain chemicals and drugs, such as levamisole (antiparasitic and anticancer drugs). Streptozotocin (STZ) is also an anticancer-antibiotic agent that has been used for decades to induce a diabetic kidney disease model in rodents. The purpose of this study is to determine if STZ causes alpha-2u globulin nephropathy in male rats during an advanced stage of diabetic kidney disease. Alpha-2u globulin nephropathy, water absorption and filtration capacities (via aquaporin [AQP]-1, - 2, - 4 and - 5) and mitochondrial function (through haloacid dehalogenase-like hydrolase domain-containing protein [HDHD]-3 and NADH-ubiquinone oxidoreductase 75 kDa subunit [NDUFS]-1 proteins) were examined in STZ-induced diabetic Wistar rat model.

RESULTS

More than 80% of severe clinical illness rats induced by STZ injection simultaneously exhibited alpha-2u globulin nephropathy with mitochondrial degeneration and filtration apparatus especially pedicels impairment. They also showed significantly upregulated AQP-1, - 2, - 4 and - 5, HDHD-3 and NDUFS-1 compared with those of the rats without alpha-2u globulin nephropathy.

CONCLUSIONS

STZ-induced alpha-2u globulin nephropathy during diabetic kidney disease in association with deterioration of pedicels, renal tubular damage with adaptation and mitochondrial driven apoptosis.

Proliferative and nonproliferative lesions of the rat and mouse urinary system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the urinary tract of rats and mice. The standardized nomenclature of urinary tract lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for urinary tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Biological responses to perfluorododecanoic acid exposure in rat kidneys as determined by integrated proteomic and metabonomic studies

Background

Perfluorododecanoic acid (PFDoA) is a perfluorinated carboxylic chemical (PFC) that has broad applications and distribution in the environment. While many studies have focused on hepatotoxicity, immunotoxicity, and reproductive toxicity of PFCAs, few have investigated renal toxicity.

Methodology/Principal Findings

Here, we used comparative proteomic and metabonomic technologies to provide a global perspective on renal response to PFDoA. Male rats were exposed to 0, 0.05, 0.2, and 0.5 mg/kg/day of PFDoA for 110 days. After 2-D DIGE and MALDI TOF/TOF analysis, 79 differentially expressed proteins between the control and the PFDoA treated rats (0.2 and 0.5 mg-dosed groups) were successfully identified. These proteins were mainly involved in amino acid metabolism, the tricarboxylic acid cycle, gluconeogenesis, glycolysis, electron transport, and stress response. Nuclear magnetic resonance-based metabonomic analysis showed an increase in pyruvate, lactate, acetate, choline, and a variety of amino acids in the highest dose group. Furthermore, the profiles of free amino acids in the PFDoA treated groups were investigated quantitatively by high-coverage quantitative iTRAQ-LC MS/MS, which showed levels of sarcosine, asparagine, histidine, 1-methylhistidine, Ile, Leu, Val, Trp, Tyr, Phe, Cys, and Met increased markedly in the 0.5 mg dosed group, while homocitrulline, α-aminoadipic acid, β-alanine, and cystathionine decreased.

Conclusion/Significance

These observations provide evidence that disorders in glucose and amino acid metabolism may contribute to PFDoA nephrotoxicity. Additionally, α_2u globulin may play an important role in protecting the kidneys from PFDoA toxicity.

Binding of perfluorooctanoic acid to rat liver-form and kidney-form alpha2u-globulins

Perfluorooctanoic acid (PFOA) is an organic fluorochemical and is reported to have a long half-life in human blood. Its urinary elimination in rats is markedly sex-dependent, and characterized by significantly longer plasma half-life of PFOA in male rats than in females. It has been postulated that male-specific PFOA binding protein(s) is responsible for the long half-life of PFOA in male rats. In this paper, two male rat specific proteins, liver- and kidney-form alpha2u-globulins (A2U(L) and A2U(K)), were purified from male rat urine and kidney, respectively. The binding of these two nroteins to PFOA was investigated using ligand blotting, electrospray ionization mass spectrometry and fluorescence competitive binding assay. The results revealed that both A2U(L) and A2U(K) were able to bind PFOA in vitro under physiological conditions, and that PFOA and a fluorescent-labeled fatty acid shared the same binding site on both A2U(L) and A2U(K). The binding affinities, however, are relatively weak. The estimated dissociation constants are in the 10(-3) M range, indicating that bindings of PFOA to either A2U(L) or A2U(K) cannot adequately explain the sex-dependent elimination of PFOA in rats, and it is unlikely that PFOA-A2U(K) binding would induce A2U nephropathy as seen with, for example, 1,4-dichlorobenzene.

Binding of brominated diphenyl ethers to male rat carrier proteins

1. Two [(14)C]-labelled brominated diphenyl ethers, 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) and decabromodiphenyl ether (BDE-209), were separately administered to the male Sprague-Dawley rat as a single oral dose (2.2 mg kg(-1) body weight and 3.0 mg kg(-1), respectively). 2. Very low [(14)C] urine excretion was observed for both congeners (<1% of the dose), and cumulative biliary excretion was approximately 4% for BDE-99 and 9% for BDE-209. 3. More than 6% of the pooled urine from the BDE-99-treated rat was protein-bound to an 18-kDa protein characterized by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western immunoblot analysis as alpha(2u)-globulin. Eighteen per cent of the radioactivity from the pooled urine from the BDE-209 treated rat was bound to albumin; no binding to alpha(2u)-globulin was detected. 4. In bile, 27-39% of the radioactivity from the BDE-99-dosed rat was bound to an unidentified 79-kDa protein, whereas essentially all (>87%) of the biliary radioactivity from BDE-209 was bound to the 79-kDa protein. Both parent BDE-99 and-209 and their metabolites were detected by thin layer chromatography in the extracted fraction of this bile protein. 5. By differential centrifugation, the subcellular localization of the (14)C derived from each congener in selected tissues was quantified. The cytosolic [(14)C] from livers of the BDE-209-treated rat was bound to a 14-kDa protein, which was characterized as a fatty acid-binding protein.

A physiological model for ligand-induced accumulation of alpha 2u globulin in male rat kidney: roles of protein synthesis and lysosomal degradation in the renal dosimetry of 2,4,4-trimethyl-2-pentanol

A physiologically based pharmacokinetic (PBPK) model was constructed for the disposition of 2,4,4-trimethyl-2-pentanol (TMP-2-OH) in male rats and its induction of accumulation of renal alpha2u-globulin (alpha2u). The model included diffusion-restricted delivery of TMP-2-OH to compartments representing liver, lung, fat, kidney, GI tract, aggregated rapidly perfused tissues, and aggregated slowly perfused tissues. Metabolism by oxidation and glucuronidation was included for liver and kidneys. Rates of hepatic alpha2u production and resorption by renal proximal tubules were taken from the literature. Degradation of liganded alpha2u by renal lysosomal cathepsins was modeled with a Km value corresponding to the measured 30% reduction in proteolytic efficiency and with free and bound forms of alpha2u competing for access to the enzymes. Increased pinocytotic uptake of alpha2u into the kidney induces cathepsin activity. A model that ascribed renal alpha2u accumulation solely to reduced lysosomal proteolysis failed to reproduce the observed accumulation. The model could reproduce experimental observations if a transient increase in hepatic synthesis of alpha2u, stimulated by the presence of liganded alpha2u in the blood, and accelerated secretion of the protein from the liver were assumed. This model reproduces time course data of blood and kidney TMP-2-OH and renal alpha2u concentrations, suggesting that renal accumulation of alpha2u is not simply a consequence of reduced proteolytic degradation but may also involve a transient increase in hepatic alpha2u production. The model predicts increased delivery of TMP-2-OH to the kidney and consequent increased renal production of potentially toxic TMP-2-OH metabolites than would be the case if no alpha2u were present. Induced lysosomal activity and increased production of toxic metabolites may both contribute to the nephrotoxicity observed in male rats exposed to an alpha2u ligand or its precursor.

Alpha 2u-globulins in the urine of male rats: a reliable indicator for alpha 2u-globulin accumulation in the kidney

Increases in kidney-type-alpha 2u-globulin (alpha G-K, molecular weight approximately 16 kDa) were detected in the urine of male adult rats treated with d-limonene by immunoblotting analysis using an antiserum which distinguishes native-type-alpha 2u-globulin (alpha G-N, molecular weight approximately 19 kDa) from alpha G-K. When male adult rats received d-limonene by gavage (0-300 mg/kg/day) for 14 consecutive days, dose-dependent increases in urinary excretion of alpha G-K were observed at a dosage level of more than 30 mg/kg/day. This was found to be directly correlated with alterations in the concentration of renal alpha G-K as well as the accumulation of hyaline droplets in proximal convoluted tubule (PCT) epithelial cells in the kidneys. Marked elevation of urinary alpha G-K was also noted following oral treatment of adult male rats with 2,2,4-trimethylpentane (TMP), 1,4-dichlorobenzene (DCB), decalin and isophorone (ISP) by gavage (1.5 mmol/kg/day) for 7 consecutive days, again in association with increased concentrations of renal alpha G-K and hyaline droplet accumulation in renal PCT epithelial cells. However, no such increases in urinary alpha G-K were observed for male adult rats treated with nephrotoxic chemicals such as puromycin aminonucleoside (PAN) (15 mg/kg/day, s.c., 14 consecutive days) or hexachloro-1,3-butadiene (HCBD) (100 mg/kg/day, p.o., 5 consecutive days), lacking the ability to cause kidney accumulation of the hyaline droplets and alpha G-K. The findings in this study thus indicate that measurement of urinary alpha G-K can give a reliable estimates not only of the potential to cause renal accumulation of alpha 2u-globulin but also of its magnitude.

A comparison of European High Test gasoline and PS-6 unleaded gasoline in their abilities to induce alpha 2u-globulin nephropathy and renal cell proliferation

Male Fischer-344 rats were administered European High Test gasoline (EHT) (50-500 mg/kg), PS-6 unleaded gasoline (UG) (16-500 mg/kg) or 2,2,4-trimethylpentane (TMP) (0.95-30 mg/kg) by gavage for ten consecutive days. To measure cell replication, rats were exposed to [3H]thymidine continuously over the last 7 days of the exposure period. Twenty-four hours after the final dose, protein droplet (PD) accumulation, alpha 2u-globulin (alpha 2u) concentration and the nuclear labeling index (LI), as a measure of cell replication, were measured in the kidneys of control and treated rats. Dose-related increases in PD, alpha 2u and cell replication were detected in the kidneys of rats treated with either gasoline mixture or TMP. The accumulation of PD and the increase in alpha 2u was greater in the kidneys of UG- and TMP-treated rats than in the kidneys of rats treated with EHT. These differences were attributed to the higher composition of branched hydrocarbons in UG, which have been shown to be the biologically active components for these endpoints. The extent of renal cell proliferation was similar in both EHT-, UG- and TMP-treated rats. This suggests that other components besides the branched hydrocarbons are responsible for the increased renal cell replication in EHT-treated rats.

An alternative hypothesis on the role of chemically induced protein droplet (alpha 2u-globulin) nephropathy in renal carcinogenesis

Based on associations between the accumulation of protein droplets containing alpha 2u-globulin in proximal tubular epithelial cells and increased incidences of renal tubular neoplasms in male rats, it has been suggested that the carcinogenicity of chemicals that cause alpha 2u-globulin nephropathy is unique to animals that synthesize this protein. Chemicals that caused alpha 2u-globulin nephropathy and renal carcinogenicity in male rats have not been shown to produce renal tumors in animals that lack the capability for hepatic alpha 2u-globulin synthesis, including female rats, male NBR rats, or mice of either sex. Because humans do not synthesize alpha 2u-globulin it has been suggested that chemicals which cause renal toxicity associated with alpha 2u-globulin accumulation do not pose an increased cancer risk to humans. In this review on the association between alpha 2u-globulin nephropathy and renal carcinogenesis, it is apparent that (a) there are data inconsistent with the hypothesis linking these occurrences, (b) alternative mechanisms of renal toxicity and carcinogenicity are plausible, (c) data on quantitative dose-response correspondences between the various stages of alpha 2u-globulin nephropathy and renal carcinogenicity are limited, and (d) a greater understanding of the molecular changes occurring during renal carcinogenesis is needed before assuming that the current hypothesis is correct. Future research aimed at resolving issues raised in this paper should help determine whether or not the association between alpha 2u-globulin nephropathy and renal carcinogenesis represents a cause-and-effect relationship.

Biochemical basis for mouse resistance to hyaline droplet nephropathy: Lack of relevance of the α2u-globulin protein superfamily in this male rat-specific syndrome

It is well-established that binding of a chemical to alpha 2u-globulin is the rate-limiting step in the development of male rat-specific hyaline droplet nephropathy. Mice synthesize mouse urinary protein (MUP), a protein which is very similar to alpha 2u-globulin, but this protein does not render the mouse sensitive to a similar renal toxicity. Therefore, the purpose of the present study was to determine the biochemical basis for mouse resistance to hyaline droplet nephropathy. Male Fischer 344 rats and B6C3F1 mice excreted 12.24 +/- 0.60 and 14.88 +/- 0.99 mg of alpha 2u-globulin and MUP daily, indicating that quantitative differences in protein excretion were not involved in the species specificity of the nephropathy. With d-limonene as a model hyaline droplet inducing agent, both rat and mouse liver microsomes oxidized the terpene to its 1,2-epoxide (the metabolite that binds reversibly to alpha 2u-globulin in vivo), demonstrating that metabolic differences do not determine the mouse resistance to this lesion. In spite of the formation of the epoxide intermediate, no binding of [14C]d-limonene equivalents to mouse kidney proteins was observed. In contrast, about 40% of the d-limonene equivalents in male rat kidney was reversibly bound to renal proteins. The renal reabsorption of alpha 2u-globulin and MUP was markedly different, as rats reabsorbed about 60% of the total filtered load of alpha 2u-globulin, but MUP was not reabsorbed by the mouse kidney. Given the absence of MUP in mouse kidney, in vitro equilibrium saturation binding studies were also conducted to determine whether MUP could bind the epoxide metabolite. alpha 2u-Globulin bound [14C]d-limonene-1,2-oxide with an apparent Kd of 4 x 10(-7) M. However, under identical experimental conditions, MUP failed to bind the epoxide. These data indicate that two major biochemical differences between alpha 2u-globulin and MUP contribute to mouse resistance to hyaline droplet nephropathy. Under both in vivo and in vitro conditions, MUP does not bind d-limonene-1,2-oxide, the rate-limiting step in the development of the nephropathy. However, even if MUP did bind the epoxide, the fact that it is not reabsorbed into the mouse kidney precludes its involvement in a syndrome involving renal protein overload. Finally, the absence of an interaction between d-limonene, a model hyaline droplet inducer, and the protein most similar to alpha 2u-globulin suggests that no other protein in the alpha 2u-globulin superfamily is likely to cause hyaline droplet nephropathy in other species.

Quantitation of urinary alpha 2u-globulin and albumin by reverse-phase high performance liquid chromatography

A rapid, reproducible, and sensitive high-performance liquid chromatography (HPLC) method for the quantitation of alpha 2u-globulin, the major urinary protein excreted by adult male rats, and albumin has been developed. Total urinary proteins, isolated by a simple Sephadex G-25 gel filtration step, are separated and quantitated by reverse-phase HPLC on a C4 Macrosphere 300 column. The proteins are separated and eluted with a two-step gradient of acetonitrile in aqueous trifluoroacetic acid. Detection limits of 9 and 25 micrograms/mL of urine were established for albumin and alpha 2u-globulin, respectively. Quantitation of urinary excretion of the two proteins in young adult male and female rats and aging male rats showed that values obtained with this method compared favorably with values from previously developed immunological techniques. To quantitate total urinary protein excretion, we modified the Bradford protein assay to use rat urinary protein as standard. Given the established importance of alpha 2u-globulin in the development of male rat-specific nephrotoxicity and nephrocarcinogenicity, these methods should be useful for studying the renal handling of this protein under normal and nephrotoxic conditions.

Preneoplastic lesions in rodent kidney induced spontaneously or by non-genotoxic agents: predictive nature and comparison to lesions induced by genotoxic carcinogens

The current literature on non-genotoxic renal carcinogens and the associated neoplastic and preneoplastic lesions has been reviewed in order to determine their occurrence and predictive nature with regard to tumor formation. In addition the mechanisms involved in the genesis of renal tumors are discussed. A more generalized classification of preneoplastic and neoplastic renal lesions was introduced, based on studies conducted with genotoxic and non-genotoxic renal carcinogens. Reports on preneoplastic lesions were found in the literature for control animals as well as animals treated with non-genotoxic carcinogens. Due to the paucity of data regarding preneoplastic lesions in control animals and animals treated with non-genotoxic carcinogens, new data were also generated by rereading kidney slides of control animals of a randomly selected NTP study and kidney slides of male rats treated with the highest dose of ochratoxin A, one of the most potent non-genotoxic renal carcinogens known. The control slides and the slides from the ochratoxin A study indicated that the cytologic and morphologic types of preneoplastic lesions characteristically observed in bioassays using genotoxic carcinogens are also present in control animals and animals treated with non-genotoxic carcinogens. The incidence of preneoplastic lesions was low in control animals and higher in animals treated with non-genotoxic carcinogens. The diverse classifications used in the literature did not allow a direct comparison of lesions and corresponding incidences with those of the newly generated data. However, three major tendencies were observed: (a) whenever a high incidence of preneoplastic lesions was reported, renal neoplasms were also found, (b) the larger the size and the further a lesion had progressed, the higher was the probability of tumor formation, and (c) not all preneoplastic lesions are irreversible, but reversibility seemed to decrease with increasing lesion size and progression. It must be emphasized that the data available for these conclusions are limited. This is not due to the lack of adequate numbers of bioassays with non-genotoxic carcinogens, but rather to the lack of consistent reporting of data. A generalized and more widely used classification which incorporates early lesions would certainly improve the current data base on renal lesions and provide future improvements in the predictive nature of these lesions.

Characteristics of chemical binding to alpha 2u-globulin in vitro--evaluating structure-activity relationships

alpha 2u-Globulin (alpha 2u) has been shown to accumulate in the kidneys of male rats treated with 2,2,4-trimethylpentane (TMP). 2,4,4-Trimethyl-2-pentanol (TMP-2-OH), a metabolite of TMP, is found reversibly bound to alpha 2u isolated from the kidneys of these treated rats. The objectives of the following study were to characterize the ability of [3H]TMP-2-OH to bind to alpha 2u in vitro and to determine whether other compounds that cause this protein to accumulate have the same binding characteristics. Although compounds that have been shown to cause the accumulation of alpha 2u in male rat kidneys compete in vitro with [3H]TMP-2-OH for binding to alpha 2u, they do so to varying degrees. The binding affinity (Kd) of the [3H]TMP-2-OH-alpha 2u complex was calculated to be on the order of 10(-7) M. The inhibition constant values (Ki) determined for d-limonene, 1,4-dichlorobenzene, and 2,5-dichlorophenol were all in the range 10(-4) M, whereas the Ki values for isophorone, 2,4,4- or 2,2,4-trimethyl-1-pentanol, and d-limonene oxide were determined to be in the range 10(-6) and 10(-7) M, respectively. TMP and 2,4,4- and 2,2,4-trimethylpentanoic acid did not compete for binding. This suggests that other factors, besides binding, are involved in the accumulation of alpha 2u. In this study the ability of a chemical to bind to alpha 2u was used as a measure of biological activity to assess structure-activity relationships among the chemicals tested and known to cause the accumulation of alpha 2u. The results so far suggest that binding is dependent on both hydrophobic interactions and hydrogen bonding.

A methylsulphonyl metabolite of a polychlorinated biphenyl can serve as a ligand for alpha 2mu-globulin in rat and major-urinary-protein in mice

1. Kidneys from rats given an intraperitoneal dose of 4,4'-bis[( 3H]methylsulphonyl)-2,2',5,5'- tetrachlorobiphenyl[(CT3SO2)2TCB)] contained (CT3SO2)2TCB associated with a protein which has been isolated and characterized by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblot and immunodiffusion analysis to be alpha 2 mu-globulin (alpha 2 mu). 2. The same radioactive alpha 2 mu-globulin complex was isolated from urine of rats given an i.p. dose of (CT3SO2)2TCB. This complex represented 12.3% (0.27% dose) and 9.3% (0.06% dose) of the radioactivity excreted in 0-24 h and 24-48 h urine, respectively. 3. The radioactivity was extractable from alpha 2 mu and characterized by t.l.c. (co-chromatography in two solvent systems) to be (CT3SO2)2TCB. 4. A radioactive-protein complex was isolated from urine of mice given an i.p. dose of (CT3SO2)2 TCB. The radioactive-protein complex was characterized to be mouse major urinary protein (MUP) by SDS-PAGE, immunoblot and immunodiffusion analysis. This complex was not detected in mouse kidney. 5. Urinary excretion of radioactive-MUP complex represented 51.7% (2.3% dose) and 28% (1.3% dose) of the radioactivity excreted in 0-24 h and 24-48 h urine, respectively.

Methylsulphone metabolites of m-dichlorobenzene as ligands for alpha 2u-globulin in rat kidney and urine

1. Kidneys from rats given oral doses of either 3,5- or 2,4- dichlorophenyl[14C]methylsulphide contained the corresponding sulphones that were associated with a protein which has been isolated and characterized by SDS-polyacrylamide gel electrophoresis and immunoblot analysis to be alpha 2u-globulin. 2. The same methylsulphone-alpha 2u-globulin complex was isolated from the urine from rats doses with 3,5-dichlorophenyl[14C]methylsulphide (0.3-1.0% of dose, 8.5% of 14C in urine. 3. The stoichiometry of binding of the isolated methylsulphone-alpha 2u-globulin complex was shown to be 0.54-0.78 nmol/nmol protein. This binding was not covalent.

Alpha 2U-globulin: measurement in rat kidney and relationship to hyaline droplets

The concentration of renal alpha 2U-globulin increased in a dose-dependent manner in adult male but not female rats which received a single dose of 2,2,4-trimethylpentane (TMP). After administration of a single dose of 12 mmol TMP/kg to adult male rats, the renal concentration of alpha 2U-globulin reached a peak at 48 hours and returned to near background level after 7 days. These changes in renal alpha 2U-globulin concentration were closely paralleled by changes in renal hyaline droplet formation. Renal alpha 2U-globulin and hyaline droplets were absent in normal pre-puberty male rats, and neither could be stimulated by a single dose of TMP. alpha 2U-Globulin was localised in the renal cortex of adult male rats, in particular the S2 segment of the proximal tubule. A greater staining intensity due to alpha 2U-globulin was seen in the S2 and adjacent segments after a single dose of TMP. A strong association is suggested between the presence of renal hyaline droplets and the occurrence of alpha 2U-globulin.

Isoparaffinic solvent-induced nephrotoxicity in the rat

Prolonged inhalation exposure to 6.5 mg/l of an isoparaffinic solvent consisting of saturated aliphatic hydrocarbons (SAHC) resulted in both functional and morphological renal changes in male rats to the exclusion of female or castrated rats. Functionally, the increased excretion of lactate dehydrogenase in the absence of an increased beta-N-acetyl-D-glucosaminidase excretion together with a decreased urinary concentrating ability upon water deprivation and slower antinatriuretic response when the sodium intake is abruptly reduced, suggest a distal tubular alteration. beta 2-Microglobulin excretion is unchanged indicating good proximal tubular cell function. The increased excretion of albumin and slightly lowered glomerular filtration rate suggest a moderate glomerular impairment. Light microscopy shows prominent hyaline droplet accumulation in proximal tubular cells and a few scattered foci of regenerative epithelia in both proximal and distal cells of the deep cortex. The urinary clearance of the major male rat urinary protein, alpha 2u-globulin, is similar in control and exposed rats but the latter have a 10-fold greater renal accumulation of this protein while the hepatic levels are identical in both groups. It is concluded that SAHC exposure causes moderate and reversible tubular and also glomerular changes in the male rat kidney.

Spontaneous nephropathies in rats

Spontaneously occurring diseases of the kidneys are very common in laboratory rats. These diseases include chronic progressive nephrosis, nephrocalcinosis, renal tubular epithelial hyaline droplets, renal tubular hypertrophy, and renal tubular basophilia. As increasing numbers of rats are used in long-term toxicity and carcinogenicity studies, recognizing spontaneously occurring renal lesions and understanding their etiology and pathogenesis are important in making an assessment of the safety of drugs and chemicals that are being tested. The purpose of this paper is to review the incidence, morphology, and pathogenesis of these spontaneous diseases. Some of the factors that alter the incidence and/or severity of these spontaneous diseases will also be discussed.

Renal function and laboratory evaluation

This paper reviews the normal renal function in relation to common functional tests helpful to detect nephrotoxicity. The measurement of renal blood flow, intrarenal distribution of blood flow, and glomerular filtration rate remain the basic parameters of nephrotoxicity. Renal tubular function is accurately measured by standard clearance tests for solutes including electrolytes, glucose and amino acids. The renal concentrating capacity serves as a sensitive but non-specific measure of renal integrity. The measurement of plasma concentration of some solutes is helpful to identify nephrotoxicity, but is most effective when a profile of solutes is measured over a time period. Urinary protein excretion and particularly the excretion of enzymes may localize the nephrotoxicity in certain tubular segments. Due to the multiple functions of the kidney, no single test or group of tests can be relied upon to detect nephrotoxicity. A battery of tests including screening tests and specific tests to measure glomerular or tubular function must be selected to match the pattern of nephrotoxicity.

Studies on the effect of corticosterone treatment on testicular activity, serum concentration of gonadotrophins, testosterone and alpha 2 u-globulin in rats pre-treated with estrogen

Adult male rats were treated with estradiol-17 beta (50 micrograms/100 g body wt./day) for 7 days. When the animals were killed 14 days later, the levels of serum gonadotrophins, testosterone and alpha 2u-Globulin as well as the weight of sex organs were reduced, testicular 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity was also suppressed; spermatogenesis was inhibited. Administration of corticosterone (2 mg/day) for 14 days to estrogen-treated rats increased the concentration of gonadotrophins, testosterone and alpha 2u-globulin in the serum. The weight of accessory sex organs and spermatogenesis appeared to be normal while 17 beta-HSD activity increased in estrogen-treated rats after treatment with corticosterone. It is concluded that corticosterone has an effect on testicular function by inducing alpha 2u-globulin and gonadotrophins in estrogen treated rats.