Identification of rat urinary proteins by zone and immunoelectrophoresis

Selection and characterization of DNA aptamers for the rat major urinary protein 13 (MUP13) as selective biorecognition elements for sensitive detection of rat pests

Among invasive mammalian predators, rats represent a major threat, endangering ecosystem functioning worldwide. After rat-control operations, detecting their continued presence or reinvasion requires more sensitive and lower cost detection technologies. Here, we develop a new sensing paradigm by using a specific rat urine biomarker (MUP13) to unambiguously signal the presence of rats. As the first step towards a new remote surveillance technology, aptamers were selected to MUP13 using the Flu-Mag SELEX method. Six aptamer candidates were initially screened by dot blot and two of them (Apt-2.5 and Apt-1.4) exhibited high affinity and specificity. Both aptamers were further characterized by bead-based assay to confirm affinity and selectivity. The lead aptamer candidates were then applied to fluorescence anisotropy (FA) and surface plasmon resonance (SPR)-based biosensor platforms, showing dissociation constants in the nanomolar range and high specificity towards their target. The SPR biosensor had limits of detection of 13.8 and 7.5 nM for Apt-2.5 and Apt-1.4, respectively, which are more than three orders of magnitude lower than the physiological concentrations found in rat urine. Selectivity of the aptamers, when comparing with other major urinary proteins, was excellent, indicating strong efficacy in specific detection of rats. In order to validate the aptamer Apt-2.5 for use with real world samples a FA-based assay was performed on a rat urine sample. The assay showed that the aptamer could detect recombinant MUP13 spiked in filtered urine and the natural MUP13 in unfiltered urine, as a first step into translation to real world application. These are the first known assays to detect and quantify a MUP biomarker of rats.

Molecular complexity of the major urinary protein system of the Norway rat, Rattus norvegicus

Major urinary proteins (MUP) are the major component of the urinary protein fraction in house mice (Mus spp.) and rats (Rattus spp.). The structure, polymorphism and functions of these lipocalins have been well described in the western European house mouse (Mus musculus domesticus), clarifying their role in semiochemical communication. The complexity of these roles in the mouse raises the question of similar functions in other rodents, including the Norway rat, Rattus norvegicus. Norway rats express MUPs in urine but information about specific MUP isoform sequences and functions is limited. In this study, we present a detailed molecular characterization of the MUP proteoforms expressed in the urine of two laboratory strains, Wistar Han and Brown Norway, and wild caught animals, using a combination of manual gene annotation, intact protein mass spectrometry and bottom-up mass spectrometry-based proteomic approaches. Cluster analysis shows the existence of only 10 predicted mup genes. Further, detailed sequencing of the urinary MUP isoforms reveals a less complex pattern of primary sequence polymorphism in the rat than the mouse. However, unlike the mouse, rat MUPs exhibit added complexity in the form of post-translational modifications, including the phosphorylation of Ser4 in some isoforms, and exoproteolytic trimming of specific isoforms. Our results raise the possibility that urinary MUPs may have different roles in rat chemical communication than those they play in the house mouse. Shotgun proteomics data are available via ProteomExchange with identifier PXD013986.

Down-regulation of alpha-2u globulin in renal mitochondria of STZ-induced diabetic rats observed by a proteomic method

AIM

To identify the changes of mitochondrial protein expression in diabetic renal parenchyma and to characterize their molecular functions and biological processes in diabetes.

METHODS

Mitochondrial proteins extracted from renal parenchyma mitochondria of streptozotocin-induced diabetic rats and normal rats were separated by two-dimensional polyacrylamide gel electrophoresis and identified by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry.

RESULTS

Eleven proteins from 533 visualized protein spots displayed significant different expressions in mitochondria of diabetic kidneys compared with those in normal ones. Among these altered proteins, two proteins with the most obvious changes in protein expression were identified as alpha-2u globulin (mature protein, named A2) and its proteolytically modified form (named A2-fragment) respectively. These proteins were found in mitochondria of male rat renal parenchyma and were proved to be down-regulated in diabetic rats simultaneously.

CONCLUSION

Our results suggest that down-regulation of alpha-2u globulin may be associated with an abnormal β-oxidation of long-chain fatty acids during diabetes. The decreased expression of A2-fragment in renal mitochondria of diabetic nephropathy may reduce fatty acid β-oxidation, which leads to a diminished energy supply from mitochondria to kidney tissue and the deposition of a large number of fatty acids in the kidney, ultimately causing and aggravating kidney damage. In conclusion, these findings may be helpful for understanding the molecular mechanism of diabetic nephropathy.

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.

Species specificity in major urinary proteins by parallel evolution

Species-specific chemosignals, pheromones, regulate social behaviors such as aggression, mating, pup-suckling, territory establishment, and dominance. The identity of these cues remains mostly undetermined and few mammalian pheromones have been identified. Genetically-encoded pheromones are expected to exhibit several different mechanisms for coding 1) diversity, to enable the signaling of multiple behaviors, 2) dynamic regulation, to indicate age and dominance, and 3) species-specificity. Recently, the major urinary proteins (Mups) have been shown to function themselves as genetically-encoded pheromones to regulate species-specific behavior. Mups are multiple highly related proteins expressed in combinatorial patterns that differ between individuals, gender, and age; which are sufficient to fulfill the first two criteria. We have now characterized and fully annotated the mouse Mup gene content in detail. This has enabled us to further analyze the extent of Mup coding diversity and determine their potential to encode species-specific cues.

Our results show that the mouse Mup gene cluster is composed of two subgroups: an older, more divergent class of genes and pseudogenes, and a second class with high sequence identity formed by recent sequential duplications of a single gene/pseudogene pair. Previous work suggests that truncated Mup pseudogenes may encode a family of functional hexapeptides with the potential for pheromone activity. Sequence comparison, however, reveals that they have limited coding potential. Similar analyses of nine other completed genomes find Mup gene expansions in divergent lineages, including those of rat, horse and grey mouse lemur, occurring independently from a single ancestral Mup present in other placental mammals. Our findings illustrate that increasing genomic complexity of the Mup gene family is not evolutionarily isolated, but is instead a recurring mechanism of generating coding diversity consistent with a species-specific function in mammals.

Semi-quantitative immunohistochemical analysis of male rat-specific alpha2u-globulin accumulation for chemical toxicity evaluation

We purified male rat urinary alpha(2u)-globulin, prepared the antibody in rabbits, and improved an immunohistochemical detection method using this antibody for male rat-specific alpha(2u)-globulin accumulation appearing as hyaline droplets in the kidneys. Our prepared antibody reacted specifically with alpha(2u)-globulin in both immunohistochemical and Western blotting analyses, furthermore, and the graded immuno-reactivities on the slide were well associated with computational image analyzing results. Using this method, we retrospectively analyzed the renal sections from the toxicity studies of 12 nephrotoxic chemicals, which had already been conducted under the Japanese Existing Chemicals Survey Program. We demonstrated that the hyaline droplets induced by treatment with 10 chemicals (1,4-dibromobenzene, dicyclopentadiene, 3,4-dimethylaniline, 1,4-dicyanobenzene, tetrahydrothiophene-1,1-dioxide, 1,3-dicyanobenzene, acenaphthene, 3,4-dichloro-1-butene, 3a,4,7,7a-tetrahydro-1H-indene and 3,5,5-trimethylhexan-1-ol) were directly associated with alpha(2u)-globulin accumulation. This immunohistochemical method is convenient for applying, even retrospectively, paraffin sections from general toxicity studies and could be useful for qualifying male rat-specific hyaline droplets consisting of alpha(2u)-globulin and renal risk in humans.

Initial induction and subsequent reduction of alpha(2u)-globulin in urine and serum of mature male rats after repeated intraperitoneal injections of (anti)estrogen

The influence of sex (anti)hormones on expression of alpha(2u)-globulin (a2uG) is complex and has not been sufficiently detailed. In order to assess the specificity of sex (anti)hormone action on a2uG expression and the utility of this approach as a sensitive screening method, mature male rats were given daily intraperitoneal injections of 17beta-estradiol (E2), dihydrotestosterone (DHT), tamoxifen (TX) and flutamide (FL) for 5 consecutive days. They were employed as representatives of estrogen, androgen, antiestrogen and antiandrogen categories, respectively. Urinary a2uG was specifically altered with E2 (1 microg/kg/day) and TX (50 mg/kg/day), but not by DHT (1 mg/kg/day) or FL (50 mg/kg/day). E2 and TX temporarily increased urinary a2uG on days 1 or 2, and days 2-4, respectively, followed by a return to the control level, and then a decrease with E2. The reduction in urinary a2uG on day 6 was more pronounced than the drop in serum a2uG. Serum hormone levels, and liver and testis weights were not remarkably altered with any treatment. Another strong xenoestrogen, diethylstilbestrol, also significantly reduced urinary and serum a2uG at 1 mg/kg/day on day 6. However, the other xenoestrogens (100 mg/kg/day of bisphenol A, nonylphenol, and dichlorodiphenyltrichloroethane, and 10 mg/kg/day of dieldrin) and phytoestrogens (10 mg/kg/day of genistein and daidzein) were without any appreciable influence. The results indicate that urinary a2uG is a sensitive indicator of estrogen action in mature male rats, with two different responses, initial induction and subsequent reduction.

Molecular evidence of complex tissue- and sex-specific mRNA expression of the rat alpha(2u)-globulin multigene family

alpha(2u)-Globulin is well known to be a rat protein encoded by a highly homologous multigene family with more than twenty members. We report here the cloning and identification of major alpha(2u)-globulin mRNA species expressed in various tissues. Initially, eight individual clones (PGCL1-8) were obtained from a male preputial gland cDNA library. Data base analysis with BLAST demonstrated six mRNAs to be novel, all clones being characterized by highly conserved sequence motifs as lipocalins. All cDNAs contained an open reading frame of 543 nucleotides and encode 181 amino acid proteins showing 92.5-98.7% and 87.3-98.3% nucleic and amino acid identity, respectively. Denaturing gradient gel electrophoresis (DGGE) with sequence analysis showed that PGCL4 is a major member in the female mammary gland, and in the submaxillary and lachrymal glands of both sexes, while the counterpart in male liver and the coagulate glands was found to be PGCL1. Numbers of cDNA species including PGCL1 and PGCL4 were found in preputial glands, no sex-related difference being observed. These results directly demonstrate complex tissue- and sex-specific expression of alpha(2u)-globulins in terms of mRNA species, providing useful information for understanding regulation of the alpha(2u)-globulin multigene family.

Proteomics to display lovastatin-induced protein and pathway regulation in rat liver

Lovastatin is a lipid lowering agent that acts by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a key regulatory enzyme in cholesterol biosynthesis. In this study the pattern of gene network regulation induced in hepatic proteins as a response to lovastatin treatment was analyzed by proteomics. In livers of male F344 rats treated with 1.6 mg/kg/day lovastatin or 150 mg/kg/day lovastatin for seven days, 36 proteins were found to be significantly altered (p<0.001) in relation to treatment. The changed proteins were classified according to their cellular function and participation in biochemical pathways. The following observations were made: (i) inhibition of HMG-CoA reductase provoked a regulatory response in the cholesterol synthesis pathway including the induction of cytosolic HMG-CoA synthase and of isopentenyl-diphosphate delta-isomerase, (ii) manipulation of the lipid metabolism triggered alterations in key enzymes of the carbohydrate metabolism, and (iii) lovastatin treatment was associated with signs of toxicity as reflected by changes in a heterogeneous set of cellular stress proteins involved in functions such as cytoskeletal structure, calcium homeostasis, protease inhibition, cell signaling or apoptosis. These results present new insights into liver gene network regulations induced by lovastatin and illustrate a yet unexplored application of proteomics to discover new targets by analysis of existing drugs and the pathways that they regulate.

Mapping of IgE binding regions in the major rat urinary protein, alpha 2u-globulin, using overlapping peptides

Exposure to laboratory animals poses a hazard for development of occupational allergy. Identification of antigenic determinants of allergenic proteins may be valuable for immunotherapeutic purposes. Overlapping peptides of the major allergen in rat urine, Rat n 1.02, corresponding to the protein alpha2u-globulin were synthesised on solid support and screened simultaneously to locate IgE binding linear epitopes using a simple modified ELISA procedure. Thirty-nine peptides were synthesised, each 8 amino acids long with 4 amino acids overlaps. Sera from fifteen rat-sensitized subjects were analyzed and as controls sera from 7 non-rat-sensitized individuals were used. In general low binding and a great individual variation between sera from rat allergic individuals were seen. Some peptides were more frequently recognized by IgE antibodies in sera from rat allergics. These peptides were mainly clustered towards the N-terminal and C-terminal parts of the protein. Taken together our data suggest the existence of linear IgE binding epitopes in the rat urine allergen, Rat n 1.02. However, the role of these sequences in the allergic reaction needs further investigation.

Effect of continual light deprivation and alpha-2u-globulin replacement therapy on serum concentration of gonadotropins and testicular activity in rats

Prolonged darkness caused a fall in testicular 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity and diminished spermatogenesis, serum levels of gonadotropins, testosterone and alpha 2u-globulin. Administration of alpha 2u-globulin at a dose of 1.5 mg rat-1 per day for 7 days after 68 days of light deprivation, reversed the 17 beta-HSD activity and serum levels of gonadotropins, testosterone and alpha 2u-globulin, while spermatogenesis was restored to normal. The animals kept in prolonged darkness for 68 days and then received saline (7 days in light-dark cycle, 14 L: 10 D), showed no significant changes of testicular activity, serum levels of gonadotropins, testosterone and alpha 2u-globulin, when compared with dark-exposed animals (68 days) receiving rabbit serum (7 days in light-dark cycle, 14 L: 10 D). These results suggest that alpha 2u-globulin plays an important role in testicular function in dark-exposed rats by inducing gonadotropins and testosterone secretion.

Protein variability in male and female Wistar rat liver proteins

In the emerging field of mechanistic toxicology, growing attention is being paid to the interpretation of sex-related toxic responses. The Wistar rat outbred stock is a frequently used rodent for toxicity testing. Outbred strains, which display a relatively high degree of genetic variability between the individual animals are often used in risk assessment, as they are considered to best approximate the variability present in a human population. In this study two-dimensional (2-D) protein gel electrophoresis was applied to investigate the liver protein patterns of male and female Wistar rats and to search for (i) sex-related and (ii) interindividual qualitative and quantitative differences in protein expression. Among the sexes, six proteins were detected that were shown to be exclusively present in male rats and one that was present only in females. A male-specific protein was tentatively assigned to alpha 2u globulin. Seven protein spots showed statistically significant abundance changes (p < 0.001) between males and females, one was tentatively assigned to heme oxygenase 1 and another to the 23 kDa morphin-binding protein. Four sets of protein spots were detected that showed positional shifts in the individual patterns and are likely to represent polymorphic proteins inherent in the Wistar rat. These results form a valuable basis for future investigations of drug-induced changes in the male and female Wistar rat liver pattern.

Degree of ethoxyquin-induced nephrotoxicity in rat is dependent on age and sex

The toxicity of ethoxyquin (EQ) to rat kidney was examined in males which were either weanling or adult at the beginning of the experiment, and also in adult females. Female rats were much less susceptible to the toxic effects of EQ than males of the same age. In males damage to the cortex, mainly as an acceleration of the normal ageing process, was similar in both age groups, but rats exposed to EQ as weanlings also suffered from extensive papillary necrosis. Male rats were more prone than females to proteinuria, which was greatly exacerbated by EQ in both age groups. Thus there is very little evidence of nephrotoxicity in adult female rats on exposure to EQ at 0.5% in the diet for 26 weeks. In males, the initial age of the animal, as well as the length of treatment, influences the extent of damage.

Castration inhibits glomerular hypertrophy and proteinuria in uninephrectomized male rats

Renal mass reduction may lead to glomerular hypertrophy, proteinuria and focal glomerulosclerosis (FGS) in humans and rats. In humans and rats, females are less susceptible than males to these phenomena. This study was undertaken to evaluate the effect of male rat castration on the pathogenesis of proteinuria and FGS. Urinary protein was measured in 60-day-old male and female rats. Uninephrectomy was performed in all rats, and castration in half of the males. After 180 days, proteinuria, glomerular filtration rate (GFR) and blood biochemistry were determined. Kidneys were resected, weighed and subjected to morphologic studies. Following uninephrectomy, male rats developed severe proteinuria: 132.3 +/- 40.9 mg 24 h-1, most of which was accounted for by an albuminuria of 70.9 +/- 19.3 mg 24 h-1. In contrast, protein excretion in female and castrated male rats remained within normal limits: 8.0 +/- 1.8 and 4.2 +/- 0.5 mg 24 h-1, respectively. Mean glomerular volume in male rats was 1.18 +/- 0.08 x 10(6) microns3; much higher than in female rats, 0.84 +/- 0.04 x 10(6) micron3, and castrated male rats, 0.87 +/- 0.03 x 10(6) micron3 (P less than 0.005). On light and electron microscopy, glomeruli of female and castrated male rats were completely normal. In contrast, in four of seven male rats, mild glomerular changes were observed. They consisted mainly of mesangial expansion, electron-dense deposits and collapse of capillary loops. These data suggest that castration confers protection against the development of glomerular hypertrophy and proteinuria in uninephrectomized male rats. Endogenous testosterone may be associated with this development.

Length heterogeneity in rat salivary gland alpha 2 mu globulin mRNAs: multiple splice-acceptors and polyadenylation sites

Rat alpha 2 mu globulins are coded for by a family of about 25 structurally related genes, some of which are expressed in the male adult liver while the other subset seems to be active in several excretory organs, including salivary and lacrymal glands. To estimate the number and specificity of genes expressed in the salivary glands, we determined nucleotide sequences of 30 cDNA clones. At least two alpha 2 mu globulin genes are active and two thirds of mRNAs were shown to code for the peptide two amino acids shorter than the others. Unexpected observation was the intense length polymorphism in the 3' non-coding 6th intron-7th exon regions presumably caused by alternative splice-acceptor selection. At least six acceptor sites were utilized and the longest type retained the entire 6th intronic sequence resulting in a formation of unusually longer product. A stable mRNA molecule of this type was demonstrated in salivary glands by Northern blotting probed with the 6th intron-specific fragment. Together with three independent polyadenylation sites, the rat salivary glands generate a diverse set of alpha 2 mu globulin mRNAs.

Tissue-specific and hormonally regulated expression of a rat alpha 2u globulin gene in transgenic mice

To investigate the tissue-specific and hormonal regulation of the rat alpha 2u globulin gene family, we introduced one cloned member of the gene family into the mouse germ line and studied its expression in the resulting transgenic mice. Alpha 2u globulingene 207 was microinjected on a 7-kilobase DNA fragment, and four transgenic lines were analyzed. The transgene was expressed at very high levels, specifically in the liver and the preputial gland of adult male mice. The expression in male liver was first detected at puberty, and no expression was detected in female transgenic mice. This pattern of expression is similar to the expression of endogenous alpha 2u globulin genes in the rat but differs from the expression of the homologous mouse major urinary protein (MUP) gene family in that MUPs are synthesized in female liver and not in the male preputial gland. We conclude that these differences between rat alpha 2u globulin and mouse MUP gene expression are due to evolutionary differences in cis-acting regulatory elements. The expression of the alpha 2u globulin transgene in the liver was abolished by castration and fully restored after testosterone replacement. The expression could also be induced in the livers of female mice by treatment with either testosterone or dexamethasone, following ovariectomy and adrenalectomy. Therefore, the cis-acting elements responsible for regulation by these two hormones, as well as those responsible for tissue-specific expression, are closely linked to the alpha 2u globulin gene.

Tissue-specific and hormonally regulated expression of a rat alpha 2u globulin gene in transgenic mice

To investigate the tissue-specific and hormonal regulation of the rat alpha 2u globulin gene family, we introduced one cloned member of the gene family into the mouse germ line and studied its expression in the resulting transgenic mice. Alpha 2u globulingene 207 was microinjected on a 7-kilobase DNA fragment, and four transgenic lines were analyzed. The transgene was expressed at very high levels, specifically in the liver and the preputial gland of adult male mice. The expression in male liver was first detected at puberty, and no expression was detected in female transgenic mice. This pattern of expression is similar to the expression of endogenous alpha 2u globulin genes in the rat but differs from the expression of the homologous mouse major urinary protein (MUP) gene family in that MUPs are synthesized in female liver and not in the male preputial gland. We conclude that these differences between rat alpha 2u globulin and mouse MUP gene expression are due to evolutionary differences in cis-acting regulatory elements. The expression of the alpha 2u globulin transgene in the liver was abolished by castration and fully restored after testosterone replacement. The expression could also be induced in the livers of female mice by treatment with either testosterone or dexamethasone, following ovariectomy and adrenalectomy. Therefore, the cis-acting elements responsible for regulation by these two hormones, as well as those responsible for tissue-specific expression, are closely linked to the alpha 2u globulin gene.

Homology between the pyrazine-binding protein from nasal mucosa and major urinary proteins

Sequence analysis of the pyrazine-binding protein from bovine olfactory mucosa reveals marked homology with a family of proteins of unknown function found in the urine of the adult male mouse and rat. In view of the dramatic biological responses to odorants transmitted in male rodent urines, it is proposed that these proteins play important roles in some aspects of odor transmission and reception.

The complete amino acid sequence of human serum retinol-binding protein

The complete amino acid sequence of human serum Retinol-binding protein (RBP) including the distribution of its three disulfide bridges, has been determined. The protein consists of 182 amino acid residues, the order of which was determined following the isolation of five CNBr-fragments. Direct amino acid sequence analysis in an automatic liquid phase sequencer provided almost the entire sequences of the five CNBr-fragments. Several sets of enzymatically derived peptides of RBP were also used to elucidate the primary structure. RBP displays significant homology to bovine beta-lactoglobulin, human alpha 1-microglobulin and rat alpha 1-microglobulin. RBP contains an internal homology. Thus, residues 36 to 83 display statistically significant homology with residues 96 to 141.

Developmental and hormonal regulation of alpha 2u-globulin gene transcription

Hepatic alpha 2u-globulin protein and RNA levels are under developmental and complex multihormonal control. The present studies directly evaluate the degree to which this regulation is transcriptional. alpha 2u-Globulin transcription was determined by measuring nuclear runoff RNA in vitro, and tissue alpha 2u-globulin mRNA levels were measured by dot blot hybridization. These studies reveal that (i) in male rats the transcriptional rate of the alpha 2u-globulin genes increases during postnatal development; (ii) no alpha 2u-globulin transcription is detectable in hepatic nuclei derived from hypophysectomized rats; (iii) growth hormone and glucocorticoid are both absolutely required, and glucocorticoid can replace androgen for alpha 2u-globulin gene transcription in the livers of hypophysectomized male rats; and (iv) chronic treatment of mature male rats with estrogen results in a progressive decrease in the hepatic transcription of alpha 2u-globulin genes. In all instances changes in the transcriptional rate of alpha 2u-globulin genes paralleled the tissue level of alpha 2u-globulin RNA. Thus transcriptional control predominates in regulating hepatic alpha 2u-globulin RNA levels.

Species, sex, and tissue specificity in toxicologic and proliferative responses

Responsible regulatory decisions regarding the fate of new chemicals require careful evaluation of a host of health, economic, and social factors, in addition to a thorough evaluation of potential risks. In risk assessment, laboratory animals are used as human surrogates in testing for potential chemical effects since mammals are anatomically, physiologically, and biochemically similar and, in most cases, have similar responses to exogenous chemical, biologic, and physical agents (with differences in response usually quantitative rather than qualitative). Unfortunately for the sake of proper extrapolation to humans, qualitative differences do occur, resulting in species, sex, and/or tissue specificity in toxicologic/proliferative responses. Since the toxicologic pathologist is trained in comparative medicine he/she must play a primary role in recognizing and demonstrating specificities in tissue alteration of laboratory animals by new chemicals of potential importance to society. A model exemplifying the recognition and demonstration of species, sex, and tissue specificity of test substance response will be described. In this model a presumably unique alteration of male rat kidney occurred in response to a specific class of test substances. The decision tree in establishing specificity, as well as the nature of the test substances, will be described.

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.

Different forms of alpha 2u-globulin in male and female rat urine

alpha 2u-Globulin is usually considered to be present only in male rat urine. This study demonstrates that a very similar protein exists in female rat urine and compares its properties with those of the male form. Isoelectric focusing followed by immunofixation reveals considerable microheterogeneity of alpha 2u-globulin in male and female rat urine. Important sex differences are noted in the banding pattern. The isoelectric point of the major male component (pI approximately equal to 5.3) is considerably higher than that of the major female components (pI approximately equal to 4.6). In addition, the female form of alpha 2u-globulin has a somewhat higher mobility on sodium dodecyl sulphate/polyacrylamide gel electrophoresis than its male counterpart. These sex differences are preserved after purification of alpha 2u-globulin from male and female rat urine by affinity chromatography and enrichment of the major male and female components by ion-exchange chromatography. Immunologically no differences are observed between these purified components and their amino acid composition reveals only minor differences. A slightly higher carbohydrate content is observed in the major female component than in the major male component. Finally evidence is presented that oestrogen treatment suppresses the male forms of alpha 2u-globulin but has no effect on the female forms. The observed differences between the male and female forms and their different hormonal control suggest that they are encoded by different genes.

Multihormonal induction of alpha 2u-globulin in an established rat hepatoma cell line

A subclone of the FU5-5 rat hepatoma cell line has been isolated which is inducible more than several hundred fold for the 20,000 dalton form of the major rat urinary protein alpha 2u-globulin. The basal relative synthetic rate (RSR) in growth medium containing 10% fetal calf serum was less than 2 X 10(-6) of total protein synthesis. Both dexamethasone and insulin were necessary for induction, and yielded a maximum induced RSR of 4-8 X 10(-3). Triiodothyronine (T3), dihydrotestosterone (DHT), rat growth hormone (GH), and estrogen, all of which have been shown to influence the induction of alpha 2u-globulin in the intact rat, were without effect on the cell line. A factor present in fetal calf serum was also necessary for maximum induction, since dexamethasone plus insulin in serum-free medium raised the RSR to only 3 X 10(-5); exogenous T3, GH, and DHT could not substitute for this serum factor. The kinetics of induction by dexamethasone were slow, with a lag of approximately 48 hr followed by a period of increasing RSR for 6-20 days. Removal of dexamethasone from induced cells led to an exponential decline in the RSR (t 1/2 15 hr). The concentrations of dexamethasone and insulin that could yield half maximum induction were 5 X 10(-8)M and 3 X 10(-11)M, respectively. Higher concentrations of insulin, although still in physiological range (10(-9)M), inhibited induction. At yet higher insulin levels, beyond the physiological range, alpha 2u-globulin synthesis returned to maximum values. The lack of DHT, T3, and GH requirement for alpha 2u-globulin induction in this cell line may mean that a regulatory aberrancy has occurred in this transformed cell line, or, alternatively, that these hormones act indirectly in the intact animal. This cell line should prove useful for the study of the molecular events associated with alpha 2u-globulin induction and for genetic approaches to the problem of multihormonal regulation of gene expression.

Hormonal regulation of a new female-specific serum protein (FP) of the laboratory rat

This paper reports evidence for a hormonal regulation of a new rat serum protein (female specific protein, FP) which is only demonstrable in female rats. Male and female rats were treated with testosterone and estrogen. The FP was assayed with immunological methods. The following results were obtained: 1. In testosterone-treated females the serum level of FP is reduced significantly 2. In estrogenized males the FP was distinctly demonstrable but not in the control males.

Cloning and sequence of several alpha 2u-globulin cDNAs

We describe a simple cloning procedure for alpha 2u-globulin that requires neither enrichment of mRNA for cloning nor purification of a specific probe for screening recombinant colonies. Total adult male liver poly(A)+RNA was used as template for cloning, and the subsequent recombinant colonies were screened by comparing hybridization to radioactive cDNA probes prepared from hepatic male and female mRNA, respectively. Almost all of the selected "male-specific" clones were later shown to contain alpha 2u-globulin sequences. This cloned alpha 2u-globulin cDNA has been shown to specifically hybridize to male rat liver RNA, which, when isolated and translated in vitro, codes for a 21,000-dalton protein (pro-alpha 2u-globulin) immunologically identical to alpha 2u-globulin. When translation occurs in the presence of pancreatic microsomes this in vitro synthesized pro-alpha 2u-globulin is processed to the 19,000-dalton mature form of alpha 2u-globulin. The nucleotide sequence of the alpha 2u-globulin cDNA has been determined, thus elucidating the complete amino acid sequence of alpha 2u-globulin and most of the hydrophobic "leader" sequence of pro-alpha 2u-globulin. The amino acid sequence deduced from the cDNA is in agreement with the partial sequence that we previously determined by sequential Edman degradation of the purified protein. alpha 2u-Globulin cDNA clones contain within the 3'-untranslated region one or both of the two putative polyadenylylation/transcription termination sites (A-A-T-A-A-A and A-A-T-T-A-A-A). Either of these can be used, generating alpha 2u-globulin mRNA species of two lengths. A codon usage analysis of the cDNA showed that, although all six leucine codons are used for the 14 leucine residues in mature alpha 2u-globulin, the seven leucines in the partial leader sequence reported are all encoded by the same codon, CTG. The primary amino acid sequence contains a unique Asn-Gly-Ser sequence, likely to be in beta-turn conformation, as the probable site of glycosylation for this glycoprotein.

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

The kidneys are an important factor in controlling the excretion of the sex-dependent protein, alpha 2u globulin, in the urine. On a protein-free diet (0% casein), when the plasma level was reduced by 60%, the daily excretion of alpha 2u in the urine was reduced from a normal of 11 mg to 0.2 mg; 97% of the alpha 2u filtered by the kidneys was reabsorbed. When a normal-protein diet (20% casein) was restored, the serum alpha 2u levels were returned to normal within 48 hours. The urinary excretion, on the other hand, remained below normal until the eighth day after repletion, whereas the renal concentrations of alpha 2u reached higher than normal values by the fourth day. Thus, during protein deficiency the kidney reduced excessive losses of protein in the urine by an almost total reabsorption of alpha 2u. On a high-protein diet (50% casein), the serum levels of alpha 2u were normal, yet its excretion was elevated 80% above the normal (20 mg/day compared with 11 mg/day). To effect this increased loss, the reabsorption of the protein was reduced to 26% of the normal.

Plasma protein handling in the rat kidney: micropuncture experiments in the acute heterologous phase of anti-GBM-nephritis

Glomerular filtration and tubular uptake of plasma proteins have been studied in the rat using micropuncture techniques. 1. Under control conditions the glomerular capillary wall is an effective barrier, only 7.6 microgram/min x 100 g BW albumin have been measured as filtered load. Four to twelve hours after i.v. injection of anti-glomerular-basement membrane serum (anti-GBM-serum sieving coefficient phi and filtered load increased in a dose-dependent manner (phi albumin in controls = 0.27 x 10(-3), after injection of 0.5 ml Antiserum phi = 0.28 x 10(-3) and 1.0 ml Antiserum phi = 2.32 x 10(-3)). 2. The tubular reabsorption capacity is almost reached under control conditions and amounts to 5.6--10.7 microgram/min x 100 g BW for albumin. Only reduced GFR (0.36 +/- 0.07 ml/min x 100 g BW) and reduced tubular flow lead to increased tubular uptake under overload conditions (10.7 vs. 99.0 microgram albumin/min x 100 g BW). 3. Tubular reabsorption of so-called high-molecular-weight proteins seems to be a nonselective mechanism. The ratio Alb/Alb + Glob (89.9--93.1%) did not differ significantly at the individual puncture sites and in the final urine.

Hormonal regulation of the hepatic messenger RNA levels for alpha2u globulin

The messenger RNA rat alpha2u globulin has been identified and quantitated in a cell-free translational system derived from Krebs II ascites cells. Hepatic tissue of the mature male rats which normally produce alpha2u globulin was also found to contain a high level of alpha2u mRNA. Approximately 1.6 per cent of all poly(A) containing RNA of the adult male rat liver could be accounted for alpha2u messenger activity. Female rats do not produce alpha2u globulin and no alpha2u mRNA activity could be detected in the poly(A) containing RNA fraction obtained from the livers of these animals. However, androgen treatment to spayed female rats was found to induce the parallel appearance to both alpha2u globulin and its corresponding mRNA. Both hypophysectomy and adrenalectomy which are known to reduce the level of alpha2u globulin in the urine of male rats were found also to reduce the hepatic level of alpha2u mRNA. The results indicate that hormonal control of alpha2u globulin synthesis in rat liver is achieved primarily through regulation of its translatable mRNA level and that more than one hormone may participate in this regulation.