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Rats are employed to investigate the role of platelets in thrombus formation under flow conditions in vivo and to evaluate the pre-clinical potential of antiplatelet drugs. While Wistar and Sprague-Dawley (SD) strains are commonly used in thrombosis models, a number of rat strains have been established. Each strain possesses genetically unique characteristics such as hypertension, hyperglycemia or hyperlipidemia. The appropriate selection of a strain might have advantages for physiological and pharmacological studies. Comparative investigation of platelet aggregation among laboratory strains of rats is useful for the development of thrombosis models. In the present study, platelet aggregation response in eight laboratory rat strains, ACI, Brown Norway (BN), Donryu, Fischer 344 (F344), LEW, SD, Wistar and WKAH, were compared. Considerable strain differences were observed in ADP-, collagen- and TRAP-induced platelet aggregation. SD and BN are high-platelet-aggregation strains, while F344 and ACI are low-response strains. In the arteriovenous shunt thrombosis model, SD formed larger thrombi than F344 and Wistar rats. In the FeCl(3)-induced thrombosis model with the carotid artery, the time to occlusion of SD was significantly shorter than of F344 and ACI rats. F344 and ACI rats had significantly increased bleeding times compared with SD rat. The present study demonstrates that there are considerable strain differences in platelet aggregation among laboratory rats, which reflect thrombus formation.

Unilateral renal agenesis (URA) is a common developmental defect in humans, occurring at a frequency of approximately 1 in 500-1,000 births. Several genetic syndromes include bilateral or unilateral renal agenesis as an associated phenotype. However, URA frequently occurs in individuals not afflicted by these syndromes and is often asymptomatic. Although it is clear that genetic factors contribute to the etiology of URA, the genetic bases of URA are poorly defined at this time. ACI rats, both males and females, exhibit URA at an incidence of 5%-15%. In this article we characterize the incidence of URA in female and male F(1), F(2), and backcross (BC) progeny from reciprocal genetic crosses between the ACI strain and the unaffected Brown Norway (BN) strain. Through interval mapping analyses of 353 phenotypically defined female F(2) progeny, we mapped to rat Chromosome 14 (RNO14) a genetic locus, designated Renag1 (Renal agenesis 1), that serves as the major determinant of URA in these crosses. Further genotypic analyses of URA-affected female and male F(2) and BC progeny localized Renag1 to a 14.4-Mb interval on RNO14 bounded by markers D14Rat50 and D14Rat12. The data from these genetic studies suggest that the ACI allele of Renag1 acts in an incompletely dominant and incompletely penetrant manner to confer URA.

Recently, we demonstrated that Type 1 and 2 spike-wave discharges (SWD) in the EEG of juvenile WAG/Rij rats were affected differently by housing before the period at which SWD start to occur. Here we consider possible sensitive periods by analyzing strain and housing influences before and after age of SWD onset. The effects of environment in WAG/Rij and ACI rats were investigated by manipulating housing during the period in which SWD become fully manifested in WAG/Rij rats. Rats were first housed from weaning in either an impoverished or enriched environment. Housing changed for half of the rats at three months, while for the other half housing stayed the same. EEG recordings at six months showed that enriched housing led to a worsening of seizure activity. The occurrence, number and mean duration of both types of discharges were influenced differently by strain, housing and age. Our data strengthen the strong genetic dependence of Type 1 SWD, but the mean duration seems to remain sensitive to housing during development. Type 2 SWD are more sensitive to environmental influences, especially in WAG/Rij rats. Moreover, the period after three months seems a sensitive period for housing effects on Type 2 SWD in this strain. Finally, our data further support the idea that Type 1 and 2 SWD are different phenomena, with their number and mean duration controlled by distinct mechanisms.

Estrogens have been inextricably linked to the etiology of breast cancer. We have demonstrated that the female ACI rat exhibits a unique propensity to develop mammary cancers when treated continuously with physiological levels of 17 beta-estradiol (E2). The E2-induced mammary cancers are estrogen dependent and exhibit genomic instability. In contrast, the genetically related Copenhagen (COP) rat strain is relatively resistant to E2-induced mammary cancers. In this study we evaluated susceptibility to E2-induced mammary cancers in first filial (F(1)), second filial (F(2)), and backcross (BC) progeny generated from reciprocal intercrosses between the ACI and COP strains. F(1) progeny resembled the parental ACI strain with respect to incidence of E2-induced mammary cancers. However, latency was significantly prolonged in the F(1) populations. These data indicate that susceptibility behaves as an incompletely dominant phenotype in these crosses. Analysis of phenotypes exhibited by the F(1), F(2), and BC populations suggests that mammary cancer susceptibility is modified by one or two genetic loci in the reciprocal intercrosses between the ACI and COP strains. Susceptibility to E2-induced mammary cancers did not correlate with E2-induced pituitary growth in the genetically diverse F(2) and BC populations, suggesting that the genetic bases for susceptibility to E2-induced mammary cancers differ from those for E2-induced lactotroph hyperplasia.

The number of genetic markers for the rat is still limited, in spite of its wide use in cancer research. To facilitate accurate mapping of both established and novel rat genetic markers, we constructed a linkage map by genotyping 105 F2 rats from ACI/N (ACI) and BUF/Nac (BUF) crosses. This map consists of 120 genetic markers that had been previously reported, mainly by two research groups, but had not been integrated. To find new genetic markers, the arbitrarily primed polymerase chain reaction (AP-PCR) was applied to detect polymorphic bands between ACI and BUF rats. After testing 56 single primers and 12 combinations of primers, we found 36 bands produced by 16 single primers and two combinations to be reliably polymorphic between ACI and BUF rats. The 36 bands were typed in the 105 F2 rats, and 29 of them could be linkage-mapped. AP-PCR is thus useful to detect new genetic markers in laboratory strains of rats.

Representational difference analysis (RDA) was applied to isolate chromosomal markers in the rat. Four series of RDA [restriction enzymes, BamHI and HindIII; subtraction of ACI/N (ACI) amplicon from BUF/Nac (BUF) amplicon and vice versa] yielded 131 polymorphic markers; 125 of these markers were mapped to all chromosomes except for chromosome X. This was done by using a mapping panel of 105 ACI x BUF F2 rats. To complement the relative paucity of chromosomal markers in the rat, genetically directed RDA, which allows isolation of polymorphic markers in the specific chromosomal region, was performed. By changing the F2 driver-DNA allele frequency around the region, four markers were isolated from the D1Ncc1 locus. Twenty-five of 27 RDA markers were informative regarding the dot blot analysis of amplicons, hybridizing only with tester amplicons. Dot blot analysis at a high density per unit of area made it possible to process a large number of samples. Quantitative trait loci can now be mapped in the rat genome by processing a large number of samples with RDA markers and then by isolating markers close to the loci of interest by genetically directed RDA.

ACI-rats are considered as a model for studying urogenital abnormalities. In order to recognise cytogenetic changes related to these abnormalities 50 male ACI/Seg rats were examined by means of gross macroscopic, histological, and karyotypical investigations. In six of the examined animals (12%) unilateral agenesis of the kidney and ipsilateral hypoplasia of the testes and seminal vesicles were observed. Isochromosome 8 and trisomy 8 (i8, +8) were observed in 26.5% of karyotypes from the animals with kidney agenesis. Chromosome heteromorphisms such as 1p+, 3p+, 11p+, 12p+ were found in animals with and without apparent pathology. Because of the similarity between the phenotypical changes found in ACI-rats and in patients with familial renal agenesis (Potter's syndrome) and hereditary renal agenesis and aplasia (HRA), rat and human chromosomes associated with manifested renal malformations were examined by comparative cytogenetics and gene mapping.

The Lewis (LEW) rat strain is highly susceptible to a large number of experimentally induced inflammatory and autoimmune diseases. The Lewis resistant (LER) rat strain, which reportedly arose as a spontaneous mutation in a closed colony of LEW rats, is resistant to many of these disorders. The mechanism of resistance is not yet clear. We report the analysis of 19 simple dinucleotide repeat polymorphisms in 13 rat strains including the LEW/N and LER/N rat strains. The LEW/N and LER/N alleles were the same in only 42% of cases. For all of the other polymorphisms, the LER/N and Buffalo (BUF/N) rat strain alleles were identical. These data provide evidence that the LER strain did not arise as a spontaneous mutation in the LEW strain but is the result of an outcross between the LEW and BUF rat strains. The LER rat strain is now a recombinant inbred rat strain. This information should facilitate the genetic analysis of the loci responsible for resistance to experimental autoimmune disease in the LER rat.

The ability of isolated skin and kidney cells to activate allogeneic lymphocytes in vitro was studied in the MHC-identical and incompatible rat strains. The preparation of these cells and optimal culture conditions were summarized. 3H-thymidine uptake was strongest with skin epidermal cells and weakest with kidney cells. The results obtained from fractionated cells indicated that both Langerhans (Ia positive) and other cells (Ia negative) of the skin epidermis stimulated lymphocytes equally well and that only glomerulus and whole kidney cells stimulated, whereas cells fom the medulla and cultured epithelium failed to do so. It was suggested that skin epidermal cells possess lymphocyte-activating antigens other than Ia antigens that may be responsible for MHC-identical graft rejection. The weaker reaction by kidney cells and the limited localization of lymphocyte-activating determinants suggest that kidney cells may not express specific alloantigens detectable by the procedure employed; these cells obviously carry only a limited amount of Ia antigens.

Alcohol dehydrogenase (EC 1.1.1.1) activity was measured in liver extracts from one outbred and three inbred strains of rats. Strain-specific differences in enzyme activity were observed in the adult male rats. The differences appeared as the animals reached puberty. Studies on the enzyme purified from Sprague-Dawley and ACI rats indicate that the enzymes in these strains are identical and that the difference in activity found in liver extracts is due to differences in the amount of enzyme present. Genetic crosses between Sprague-Dawley and ACI rats suggest that the liver content of alcohol dehydrogenase is controlled by an autosomal regulatory locus with the characteristics of a temporal gene.

The ACI rat provides a congenital mammalian model for the spontaneously occurring defects of renal agenesis and hydronephrosis. These anomalies appear to be part of a spectrum of abnormalities caused by a mesonephric duct defect. These same anomalies also exist in man probably more commonly than previously appreciated.

Immunocompetent cell functions were evaluated in spontaneously hypertensive rats (SHR). Hematological studies revealed decreased absolute numbers of lymphocytes and increases number of polynucleic cells in the peripheral blood of SHR. The SHR had a reduced number of immature T lymphocytes in their thymuses in comparison with an original strain of Wistar rats, as detected by the rosette formation test with guinea pig erythrocytes. The antibody response to sheep red blood cells (SRBC) of the 3-month-old SHR was profoundly depressed and was about one-teeth that of the Wistar rats. Cell cooperation experiments suggest that the T lymphocytes of the SHR were selectively impaired in antibody responses to SRBC in cooperation with B lymphocytes. B lymphocytes from the bone marrow of the SHR were not affected and produced normal numbers of plaque-forming units. Cyclophosphamide treatment, which selectively depletes suppressor T lymphocytes, did not enhance the delayed-type hypersensitivity response to SRBC in SHR. This may rule out the possibility of the involvement of the suppressor mechanism in the T cell depression of the SHR.

Inheritance of dermatoglyphic configurations was studied on the palmar III interdigital pad of the rat (Rattus norvegicus). Four rats from each of the WKS and ACI/N inbred strains were mated with each other, and 54 F1 and 88 F2 hybrids were obtained. In addition, 52 offspring were produced by backcross mating between F1 hybrids and WKS and ACI/N parents. Whorls were the predominant pattern in the WKS strain and triradial patterns characterized the ACI/N strains. The F1 hybrids showed a wide range of pattern types, consisting of whorls, loops, cusps, arches, and triradial patterns. These patterns were intermediate in size between the two inbred strains. The F2 hybrids presented a distribution of patterns with a similar range as the F1, but the frequencies of some types were different. Patterns in the offspring of each backcross demonstrated a slight shift towards the characteristic pattern of the parental inbred strain. No sex difference was observed. Generally, the bilateral differences were striking, with a radial direction predominating on the left palm, and an ulnar one on the right palm, respectively. This study suggests that the dermal patterns are genetically determined, but also are influenced by environmental factors, especially in the hybrids.

The class II antigens of the ACI rat were studied using both conventional alloantisera and monoclonal antibodies. By sequential immunoprecipitation experiments and cell binding studies, alloantisera were shown to contain antibodies to both the RT1.B and the RT1.D gene products. Using one- and two-dimensional gel electrophoresis, the structures of these gene products were shown to be distinguishable. The importance of these differences for the immune response and antigen presentation is discussed.

Restriction endonuclease digestion using Hind III and Msp I and Southern blot analysis of DNA from the liver of three inbred rat strains and one outbred strain using cDNA probes yields two banding patterns for the alphafetoprotein and albumin genes. Buffalo and Fischer DNA have one pattern whereas ACI had a different pattern for both genes. Sprague Dawley DNA contains fragments of both patterns suggesting heterozygosity in some individuals of this strain. These polymorphisms do not appear to be associated with any structural or biological differences in the proteins resulting from expression of these genes.

Fresh and frozen orthotopic iliac crest bone grafts in rats were studied histologically for determination of the long-term effects of histocompatibility matching and the freezing process on orthotopic bone graft incorporation. Grafts exchanged between groups of inbred rats, syngeneic or differing with respect to major or minor histocompatibility loci, were studied histologically at 20, 30, 40, 50, and 150 days after bone transplantation. A numerical histologic scoring system was developed and used by three observers for evaluation of coded hematoxylin and eosin sections. All frozen graft groups had the same fate regardless of histocompatibility relations between donors and recipients, and all grafts were inferior to fresh syngeneic grafts. Both fresh allograft groups received similar scores and initially at 20 and 30 days had scores similar to those of the fresh syngeneic groups. In the later intervals, however, the fresh allografts were inferior to the fresh syngeneic grafts and similar to the frozen groups. This is consistent with an older model describing two distinct phases of osteogenesis. In the long term, frozen syngeneic and fresh and frozen allografts across major and minor histocompatibility barriers were comparable, but all were significantly inferior to fresh syngeneic bone grafts.

Supplemental dietary calcium has been shown to reduce blood pressure in spontaneously hypertensive rats while restricted calcium diets cause an elevation in blood pressure. This latter nutrient effect has been enhanced by modest sodium restriction and is associated with a reduction in serum ionized calcium concentration. To determine whether alterations of dietary calcium and sodium have a similar influence on blood pressure in genetically normotensive rats, Fisher 344, Wistar Furth, and ACI rats were fed either a low (0.1%) calcium, low (0.25%) sodium diet or normal (1.0%) calcium, normal sodium (0.45%) diet from 4 weeks of age through 29 weeks of age. Indirect measurements of systolic blood pressure showed that only the Fisher 344 rats consistently responded to the low calcium/low sodium diets with an elevation of blood pressure. There was considerable variation in serum electrolytes across strains in the normal diets but all three strains experienced a reduction in ionized calcium and an elevation in phosphorus and magnesium on the restricted diets. In the Fisher 344 rats there were significant (p less than .05) inverse correlations among systolic blood pressure and serum ionized and total calcium concentrations and positive correlations among systolic blood pressure, phosphorus, and magnesium. There was no significant correlation between serum electrolytes and blood pressure in the other two strains. The data indicate that there is genetic variability in the blood pressure response to alterations in dietary calcium and sodium. The pattern of change in serum electrolytes across strains suggests that diet-induced alterations of serum electrolytes, specifically calcium, are not necessarily predictive of a pressor response. It would appear that some other calcium-sensitive physiological process involved in blood pressure regulation must respond differentially to calcium availability across strains.

The sequence of the 92 and 93 bp long, highly repetitive DNA fragments, isolated from EcoRI digested rat liver DNA, were determined. These fragments, designated 92 and 93, are found in equal abundance, 6.5 x 10(5) copies per haploid genome. J92 and J93 can be distinguished by their differential sensitivity to cleavage by HaeIII and HindIII, respectively, which cut the fragments at 75 and 57 bp from their mutually homologous 5'-ends. J92 and J93 are 38% and 35.4% G + C, respectively, and contain a disproportionate number of triplets complementary to stop codons in all reading frames. Three methylated sites were found in J92 while none could be detected in J93. The sequences around the m5C sites were 5'-Py-Py-m5C-G-Pu-Pu, except for one case where the second Py was replaced by an A. This site appeared to be hemimethylated. When J92 and J93 are placed in register from their mutually homologous 5'-ends, homology is 73% for the first 30 bp region and 63.5% for the total molecule. Thermal melting studies indicate sequence heterogeneity within J92 and J93 from substantial internal base mismatches. The sequences derived are therefore composite averages for the whole molecules. The Cot1/2 for the sequence was measured spectrophotometrically to be 2 x 10(-2) M/s on a DNA phosphorus basis and 2.15 x 10(-4) M/s on a mole fragment basis.