The effects of elk velvet antler consumption on the rat: development, behavior, toxicity and the activity of liver gamma-glutamyltranspeptidase

The effect of exposure to, followed by consumption of, a diet containing 10% powdered elk velvet antler (EVA) from the 18th day of gestation to the 88th day after birth was examined in male and female Fischer 344 rats. There were no teratogenic effects of EVA exposure in utero or differences in birth outcomes between pups born to regular chow fed and EVA chow fed dams. Growth curves of the EVA fed rats were identical to those of regular chow fed rats, as were developmental milestones of pinna development and eye-opening. Acoustical startle and righting reflexes, developmental and behavioral indices, were identical. Blood glucose levels were comparable in EVA chow fed and regular chow fed rats, indicating that EVA is without effect on glucose balance. There were no signs of toxicity in the EVA chow fed compared to regular chow fed rats as judged from plasma enzyme markers of liver damage: plasma levels of alanine aminotransferase were 50% lower in EVA chow fed rats compared to regular chow fed rats; and plasma levels of gamma-glutamyltranspeptidase (gammaGT) were the same. The activity of gammaGT displayed a decrease in the livers of EVA chow fed rats, more so in the male (22%) than in the female (14%), suggestive of an androgenic effect. A possible hepatobeneficial effect of the EVA induced decrease in liver gammaGT is discussed. In summary, dietary10% EVA chow is without long term effect on growth, development and behavior is non-toxic and may be hepatobeneficial.     

The Effects of Shipping on Early Pregnancy in Laboratory Rats

Although rats in various stages of pregnancy are routinely shipped by vendors, the effects of shipping on pregnancy outcomes have not been reported. This study examined the effects of shipping rats 1 day after mating. Two outbred stocks, (Crl:CD(SD), Crl:WI(Han)) and one inbred strain (F344/Crl) of rats (n = 300/strain) were mated in a vendor barrier room at 3‐month intervals five times, and either shipped the next day (total time in transit ～24 hr) or held in the room of origin until parturition. The pregnancy status, length of gestation, number of pups born per female, sex ratio of pups born, and neonatal mortality were compared between transported and nontransported rats. These pregnancy and litter parameters were also compared among strains and examined for seasonality; no seasonal effects were observed. Neonatal mortality was negligible at less than 2% in any of the groups. All sex ratios were normal. Transportation affected pregnancy rates only in the F344/Crl, in which 81.8% of the nontransported versus 70% of the transported rats had pups (p = 0.025). Overall, slightly fewer transported rats were pregnant, but they had larger litters (10.08 compared with 9.68, p = 0.02, pooling across all three strains) so produced the same numbers of pups. A total of 77 ± 8% of transported rats had gestation periods of 22 days or more compared with only 52 ± 10% in the nontransported rats. The reason for larger litters in transported females is unclear. Longer gestation in transported females may be due to facultative embryonic diapause, which might have implications for reproductive toxicology.     

A characterization of gamma-glutamyltranspeptidase in normal, perinatal, premalignant and malignant rat liver

gamma-Glutamyltranspeptidase displays the following order of activity in tissues of the Fischer 344 rat: kidney much greater than small intestine much greater than cerebral cortex = testis greater than lung much greater than liver = heart. The activity of the hepatic enzyme in rats is: 4-fold higher in females than males; 4-fold higher in male Wistar, Sprague-Dawley and Zucker rats than male Fischer 344 rats; increased 10-fold in very old vs young male Fischer 344. The hepatic enzyme displays significant species variation: the mouse and rat liver enzymes are similar and low in activity, while duck, dog, pig and beef enzymes are 7, 13, 86 and 92-fold higher, respectively, in activity than the male Fischer rat liver enzyme. A liver plasma membrane isolation procedure has been devised which selects for the sinusoidal face of the liver parenchymal cell as assessed by marker enzyme analysis: for these plasma membranes the purification of gamma-glutamyltranspeptidase is 21.5 and the recovery is 42% indicating that this is the cellular and subcellular locus of the enzyme in rat liver. The characteristics of the liver plasma membrane from female rats are: pH optimum of 8.0; classical Michaelis-Menten kinetics; Km of 1.43 mM and Vmax of 33.3 nmol X mg-1 X min-1. In Fischer 344 rats, gamma-glutamyltranspeptidase activities are elevated over adult levels in perinatal liver: in fetal liver homogenates and plasma membranes the activities are increased 179 and 109-fold, respectively. The activity peaks just after birth and declines rapidly over the first 15 postnatal days. The activity of the liver enzyme in the male Fischer 344 rat exhibits a progressive increase throughout diethylnitrosamine-induced hepatocarcinogenesis: it is increased 7.8-fold in homogenates and 5.4-fold in plasma membranes at the early premalignant stage; 74-fold in homogenates and 31-fold in plasma membranes at the later hyperplastic nodular premalignant stage; and 174-fold in homogenates and 61-fold in plasma membranes at the hepatoma stage. The gradual drop in purification during hepatocarcinogenesis is associated with the appearance of the enzyme in the blood.     

Development of the vasculature of the pars distalis in a tumor-susceptible strain of rat (Fischer 344) differs from vascular development in a non-tumor-susceptible strain (Lewis)

The development of the vasculature of the pars distalis of two strains of rat, Fischer 344 (F344) and Lewis (LEW), was followed in 16-day (16d) and 20-day (20d) fetuses, and in 1-day (1d), 5d, 20d, 50d, and 6-month-old females. No differences in the two strains were apparent in 16d fetuses; and the capillaries that were present were immature, i.e., tall, non-fenestrated endothelial cells, and were surrounded by poorly delineated pericapillary spaces. Immature capillaries also were predominant in 20d fetuses of both strains. Agranular folliculo-stellate cells were identifiable, projecting endfeet to the parenchymal basal lamina in 20d F344 fetuses, but not in LEW fetuses. Postnatally, the capillaries of LEW rats became progressively more thin-walled and fenestrated, and were surrounded by a pericapillary space that was well delimited by basal laminae at 20d. In 50d and 6-month LEW rats, capillaries were intact and surrounded by well-defined pericapillary spaces. By comparison in F344 rats, the capillaries remained more immature even in 50d rats and older. In addition, in F344 rats focal disruptions in endothelial cells and disruptions in parenchymal and capillary basal laminae were present in all postnatal stages, and a dramatic accumulation of plasma was evident within the pericapillary spaces at 20d. Endfeet processes of folliculo-stellate cells were abundant at the parenchymal basal lamina of 1d and 5d F344 neonates, but only rarely were identified in LEW neonates. Some activation of folliculo-stellate cells, i.e., increased numbers of lysosomes and dilated endoplasmic reticulum, was present in 50d F344 rats. Connective-tissue cells within the pericapillary space also were numerous and activated in F344 rats. Discrete gaps in the parenchymal basal lamina were evident subjacent to the folliculo-stellate cell endfeet in F344 rats but not in LEW rats. The vascular bed of F344 rats differs in its development from that of LEW rats. Characteristic of the F344 strain is a persistence of more immature capillaries, an inherent vascular fragility, and an activated state of folliculo-stellate cells.     

Two-year chronic bioassay study of rats exposed to a 1.6 GHz radiofrequency signal

The purpose of this study was to determine whether long-term exposure to a 1.6 GHz radiofrequency (RF) field would affect the incidence of cancer in Fischer 344 rats. Thirty-six timed-pregnant rats were randomly assigned to each of three treatment groups: two groups exposed to a far-field RF Iridium signal and a third group that was sham exposed. Exposures were chosen such that the brain SAR in the fetuses was 0.16 W/kg. Whole-body far-field exposures were initiated at 19 days of gestation and continued at 2 h/day, 7 days/week for dams and pups after parturition until weaning (approximately 23 days old). The offspring (700) of these dams were selected, 90 males and 90 females for each near-field treatment group, with SAR levels in the brain calculated to be as follows: (1) 1.6 W/kg, (2) 0.16 W/kg and (3) near-field sham controls, with an additional 80 males and 80 females as shelf controls. Confining, head-first, near-field exposures of 2 h/day, 5 days/week were initiated when the offspring were 36 +/- 1 days old and continued until the rats were 2 years old. No statistically significant differences were observed among treatment groups for number of live pups/litter, survival index, and weaning weights, nor were there differences in clinical signs or neoplastic lesions among the treatment groups. The percentages of animals surviving at the end of the near-field exposure were not different among the male groups. In females a significant decrease in survival time was observed for the cage control group.     

The effects of dietary flaxseed on the Fischer 344 rat: I. Development, behaviour, toxicity and the activity of liver gamma-glutamyltranspeptidase

The effect of exposure to, followed by consumption of, 10% flax chow from the 18th day of gestation to the 86th day after birth was examined in male and female Fischer 344 rats. Growth curves of the flax chow-fed rats were identical to those of regular chow-fed rats, as were such developmental milestones as pinna development, growth of hair and eye opening. Acoustical startle and the righting reflexes, developmental behavioural indices, were also the same. Blood glucose levels were comparable in flax chow-fed and regular chow-fed rats at all stages of development, indicating that flax is without effect on glucose balance. There were no signs of toxicity in the flax chow-fed rats since their plasma levels of alanine aminotransferase and gamma-glutamyltranspeptidase (gammaGT) were the same as those of regular chow-fed rats. The activity of gammaGT displayed an increase in the livers of flax chow-fed rats after puberty, more so in the male-four-fold-than in the female-1.38-fold. This is suggestive of an estrogenic effect which implicates an effect of an estrogenic flax lignan. An hepatobeneficial effect of the flax-induced increase in liver gammaGT is discussed. In summary, dietary 10% flax chow is without long-term effect on growth, development and behaviour, is non-toxic and may be hepatoprotective.     

Circadian modification of drug-induced teratogenesis in rat fetuses.

Pregnant Sprague-Dawley rats were injected with hydroxyurea (750 mg/kg) or physiological saline on the 12th day of gestation. Hydroxyurea and saline (control) treated groups were each composed of six subgroups injected at consecutive 4-h intervals (i.e., group 1 at 00(00), group 2 at 04(00),...). All females were injected at the same circadian phase as they were mated. The developmental age of all fetuses was 288 +/- 2 hrs at the time of injection. The fetuses were taken by caesarean section on the 20th or 21st day of gestation. Teratogenesis was greatest when hydroxyurea was administered in the light phase (light-dark 12:12 cycle). Deformity rates correlate with motor activity, mitotic rates and DNA synthesis.     

Resistance of Fischer 344 rats to deoxycorticosterone hypertension

Implantation of one 40 mg pellet of DOCA causes hypertension in the majority of young female Sprague-Dawley rats within three weeks without removal of a kidney or adding salt to the diet. Similar identically-treated Fischer 344 rats remain normotensive. If one kidney is removed and 1% saline is given to drink, the hormone dosage causes hypertension in rats of both strains, although even here Fischer 344 rats develop the disorder more slowly and less severely. It is concluded that for rat strains resistant to mineralocorticoid hypertension, sensitization is necessary for its induction, whereas for susceptible strains it is not. Fischer 344 rats appear to have higher levels of resting serum renin activity than Sprague-Dawley rats, but the relationship that this bears to hypertension susceptibility is unknown.     

Gestational choline deficiency causes global and Igf2 gene DNA hypermethylation by up-regulation of Dnmt1 expression

During gestation there is a high demand for the essential nutrient choline. Adult rats supplemented with choline during embryonic days (E) 11-17 have improved memory performance and do not exhibit age-related memory decline, whereas prenatally choline-deficient animals have memory deficits. Choline, via betaine, provides methyl groups for the production of S-adenosylmethionine, a substrate of DNA methyltransferases (DNMTs). We describe an apparently adaptive epigenomic response to varied gestational choline supply in rat fetal liver and brain. S-Adenosylmethionine levels increased in both organs of E17 fetuses whose mothers consumed a choline-supplemented diet. Surprisingly, global DNA methylation increased in choline-deficient animals, and this was accompanied by overexpression of Dnmt1 mRNA. Previous studies showed that the prenatal choline supply affects the expression of multiple genes, including insulin-like growth factor 2 (Igf2), whose expression is regulated in a DNA methylation-dependent manner. The differentially methylated region 2 of Igf2 was hypermethylated in the liver of E17 choline-deficient fetuses, and this as well as Igf2 mRNA levels correlated with the expression of Dnmt1 and with hypomethylation of a regulatory CpG within the Dnmt1 locus. Moreover, mRNA expression of brain and liver Dnmt3a and methyl CpG-binding domain 2 (Mbd2) protein as well as cerebral Dnmt3l was inversely correlated to the intake of choline. Thus, choline deficiency modulates fetal DNA methylation machinery in a complex fashion that includes hypomethylation of the regulatory CpGs within the Dnmt1 gene, leading to its overexpression and the resultant increased global and gene-specific (e.g. Igf2) DNA methylation. These epigenomic responses to gestational choline supply may initiate the long term developmental changes observed in rats exposed to varied choline intake in utero.     

Lipid metabolism and resistin gene expression in insulin-resistant Fischer 344 rats

The interrelationship between insulin and leptin resistance in young Fischer 344 (F344) rats was studied. Young F344 and Sprague-Dawley (SD) rats were fed regular chow. F344 animals had two- to threefold higher insulin and triglyceride concentrations and increased stores of triglycerides within liver and muscle. F344 animals gained more body fat. Both acyl-CoA oxidase (ACO) and carnitine palmitoyltransferase I gene expression were 20-50% less in F344 animals than in age-matched SD animals. Peroxisome proliferator-activated receptor-alpha gene expression was reduced in 70-day-old F344 animals. Finally, resistin gene expression was similar in 70-day-old SD and F344 animals. Resistin gene expression increased fivefold in F344 animals and twofold in SD animals from 70 to 130 days, without a change in insulin sensitivity. We conclude that young F344 animals have both insulin and leptin resistance, which may lead to diminished fatty oxidation and accumulation of triglycerides in insulin-sensitive target tissues. We did not detect a role for resistin in the etiology of insulin resistance in F344 animals.     

Hepatic insulin binding following in utero exposure to ethanol

Insulin binding to liver membranes has been studied in term fetuses of rats fed ethanol-containing liquid diet during pregnancy . Pair-fed and ad libitum-fed controls received liquid diet in which maltose-dextrins were substituted isocalorically for ethanol. Food consumption and body weigh gain of ethanol- imbibing dams were 35% and 70% less than their ad libitum counterparts respectively. Ethanol-fed rats also exhibited less gain in body weight than pair-fed controls despite isocalorically equivalent food intake. The number of live pups was not different among the various groups; however, liver weight of fetuses exposed to ethanol in utero was 47% less than those of the pups of ad libitum control dams and 28% less than those of the offspring of pair-fed control rats. Insulin binding to liver membranes of fetuses exposed to ethanol in utero was lower than that of ad libitum controls but was not significantly different from that of the pair-fed control animals. Average affinity profiles showed a reduction in K at all levels of receptor occupancy in the fetuses of ethanol-fed rats. For fetuses of the pair-fed group, K was reduced only at fractional occupancy below 20% but not at higher fractional occupancy. Because of the similarity of insulin binding in the fetuses of the ethanol-fed rats and their pair-fed counterparts, effects of ethanol on insulin binding cannot account for the reduced hepatic glycogen stores previously reported in term fetuses.     

Diethylnitrosamine-induced increase in gamma-glutamyltranspeptidase in rat liver: its association with thyroid hormone deficiency and its reversal by tri-iodothyronine.

1. The nodular phase of hepatic premalignancy was induced in male Fischer 344 rats by the administration of diethylnitrosamine, 200 mg/kg i.p., followed by promotion utilizing the Solt-Farber promoting regime. 2. Relative to the situation in normal non-treated control rats: the activity of gamma-glutamyltranspeptidase was found to be increased 9.42-fold in homogenate and 7.33-fold in plasma membrane fractions prepared from the livers of saline-injected control rats; and 81.37-fold in homogenates and 91.92-fold in plasma membranes prepared from the livers of diethylnitrosamine-injected rats; plasma levels of total T3 and total T4 were found to be decreased 42.06 and 47.45% in saline-injected control rats and 88.7 and 83.2% in diethylnitrosamine-injected rats, respectively. 3. An early pre-nodular phase of hepatic premalignancy was produced in young immature and mature adult male Fischer 344 rats by the administration of diethylnitrosamine, 75 mg/kg, without subsequent application of the promotion regime. 4. Relative to the situation in control rats: the activity of gamma-glutamyltranspeptidase was found to be increased in liver homogenates prepared from diethylnitrosamine-treated rats, 1.62-fold in young immature rats 1.20-fold in mature adult rats; plasma levels of total T3 were found to be reduced in diethylnitrosamine-treated rats, 28% in young immature rats 9% in mature adult rats. 5. Treatment of diethylnitrosamine-injected young immature male Fischer 344 rats at the prenodular phase of hepatic premalignancy with tri-iodothyronine at 0.005 micrograms/kg s.c. daily for 7 days reversed the diethylnitrosamine-induced increase in liver homogenate gamma-glutamyltranspeptidase activity and the decrease in plasma total T3, restoring these parameters to normal levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Developmental toxicity of the HIV-protease inhibitor indinavir in rats

BACKGROUND: Indinavir is an antiviral agent used for the treatment of HIV infection. We studied its developmental toxicity in rats. METHODS: Pregnant animals were treated orally with 500 mg indinavir/kg body weight (bw) from day 6 to 15 of gestation (once daily) or from day 9 to 11 (twice daily). Fetuses were evaluated for external and skeletal anomalies on day 21 of gestation. In addition, 19 rats were treated from day 9 of gestation to day 24 postnatally with 500 mg indinavir/kg bw once daily; a control group of 17 rats was treated with the vehicle accordingly. Developmental landmarks were recorded. Sixteen offspring each were studied on postnatal days 7, 14, 21, and 35 for hepatic enzyme activity. Liver tissue was examined by electron microscopy. RESULTS: Fetal examination on day 21 of pregnancy showed no treatment-related effects on number, weight, and viability of the fetuses; however, an increased incidence was noted in the supernumerary ribs and variations of the vertebral ossification centers in both indinavir-treated groups. Postnatal evaluation showed delayed fur development, eye opening, and descensus testis. The most striking finding was unilateral anophthalmia, observed in 7 pups (3%) from 2 out of 19 litters exposed to indinavir, but not in controls. Only minor changes in hepatic monooxygenase activities occurred in dams. Electron microscopy of liver samples showed hepatocellular inclusions of lipids and myelin figure-like structures in maternal livers and infiltration with granulocytes in offspring livers. CONCLUSIONS: Further studies on reproductive toxicity, including combinations of three or more antiretroviral agents as used therapeutically, are needed to determine the hazards of such a treatment.     

Developmental toxicity and uterotrophic studies with di-2-ethylhexyl terephthalate

BACKGROUND: These studies were conducted to evaluate the potential adverse effects of di-2-ethylhexyl terephthalate (DEHT) exposure on in utero development in mice and rats. In addition, a uterotrophic assay for estrogenic activity was conducted in sexually immature rats. METHODS: In the developmental toxicity studies, diet containing DEHT was fed to four groups of mated female Crl:CD(SD)IGS BR rats (25/group) from gestation day (GD) 0-20 or Crl:CD1(ICR) mice (25/group) from GD 0-18. Concentrations within the feed were 0, 0.3, 0.6, and 1.0% for the rats and 0, 0.1, 0.3, and 0.7% for the mice. Laparohysterectomies were carried out on the last day of exposure and the numbers of fetuses, early and late resorptions, total implantations, and corpora lutea were recorded. The fetuses were weighed, sexed, and examined for external, visceral and skeletal malformations, and developmental variations. The dose rate from dietary DEHT exposure was 0, 226, 458, and 747 mg/kg/day in the rats and 197, 592, and 1382 mg/kg/day in the mice for the control, low, mid, and high-exposure groups, respectively. RESULTS: DEHT exposure did not affect clinical observations. A slight reduction in body weight gain was noted in the high-dose level rat group; the remaining groups were unaffected. At necropsy, increased liver weights were noted in the high-dose rat group and the mid- and high-dose mouse groups. Mean numbers of implantation sites and viable fetuses, mean fetal weights, and mean litter proportions of preimplantation loss, early resorptions, late resorptions, and fetal sex ratios were unaffected by DEHT exposures. No test article-related malformations or variations were observed at any concentration level in the rat and mouse developmental toxicity studies. In the uterotrophic assay for estrogenic activity, sexually immature female rats received oral gavage doses 20, 200, or 2000 mg DEHT/kg bw/day from postnatal day (PND) 19-21. A slight reduction in rate of body weight gain was noted on the first day of dosing in the high dose group, but no other indications of toxicity were evident. DEHT exposure did not affect wet or blotted uterine weight parameters in any of these dose groups. The NOEL for developmental toxicity in rats was 747 mg/kg/day and 1382 mg/kg/day in mice. The NOEL for estrogenic activity was 2000 mg/kg/day. The NOEL for maternal toxicity was 458 mg/kg/day in rats and 197 mg/kg/day in mice. CONCLUSIONS: The lack of adverse developmental effects with DEHT exposure are in contrast to the adverse developmental effects noted after di-2-ethylhexyl phthalate (DEHP) exposure. The difference between the effects noted with the ortho-constituent (DEHP) and the lack of effects reported with the para-constituent (DEHT) is due most likely to differences in metabolism and the formation of the stable monoester, mono-2-ethylhexyl phthalate (MEHP) from the DEHP moiety.     

Effects of maternal ethanol consumption during pregnancy or lactation on intestinal absorption of folic acid in suckling rats

A fostering/crossfostering analysis of the effects of maternal ethanol exposure on jejunal and ileal folate absorption was performed. Male and female rats were randomized into two groups. In the first group, ethanol-treated rats received ad libitum 5, 10 and 15% ethanol in the drinking fluid during three successive weeks. A consumption of 20% was maintained in this group for 5 additional weeks. Ethanol-treated rats were mated. Group 2 served as the control. To study the effect of chronic alcoholism during lactation or gestation separately, at birth (2nd day postpartum) control newborns were cross-fostered to ethanol dams (EG), and the pups issued from the ethanol treated mothers were cross-fostered to control dams (CG). Thus, three experimental groups of pups were formed: (1) control pups receiving no treatment during gestation and lactation (CG); (2) pups exposed to ethanol only during gestation (GG); and (3) pups exposed to ethanol only during lactation (LG). At 21 days postpartum the jejunal and distal ileum folate absorption was determined in the offspring rats by a perfusion technique. Milk folic acid levels were determined by an immunoluminometric assay. The results showed an increase in jejunal folic acid absorption in offsprings exposed to ethanol only during the lactation period (LG). However, in pups exposed to ethanol only during the gestation period (GG), the jejunal folic acid absorption was significantly increased only at concentrations of 0.25, 0.5 and 2.5 microM. No free folic acid absorption occurred in the distal ileum of control pups (CG) at day 21 at all assayed concentrations but in offsprings exposed to ethanol only during the gestation or lactation periods absorption did take place. Pups exposed to ethanol during the gestation period (GG) showed decreased values in ileum folic acid absorption at the lowest assayed concentration (0.25 microM) compared to values obtained for pups exposed to ethanol only during lactation (LG). Milk folic acid levels were significantly decreased in the ethanol-fed dams on day 21 of lactation. These results indicate that exposure of rats to ethanol during the lactation period affects more severely postnatal development of intestinal functions than ethanol exposure only during gestation. In summary, both the exposure to ethanol itself and the decrease in folic acid intake caused alterations in the function of the intestinal mucosa in the offspring, which in turn altered absorption time and development. However, the present results do not explain how ethanol stimulated intestinal absorption of folic acid in pups exposed to ethanol during the gestation or lactation periods. Further studies are needed.     

Iron absorption by Belgrade rat pups during lactation

Divalent metal transporter-1 (DMT1) mediates dietary nonheme iron absorption. Belgrade (b) rats have defective iron metabolism due to a mutation in the DMT1 gene. To examine the role of DMT1 in neonatal iron assimilation, b/b and b/+ pups were cross-fostered to F344 Fischer dams injected with (59)FeCl(3) twice weekly during lactation. Tissue distribution of the radioisotope in the pups was determined at weaning (day 21). The b/b pups had blood (59)Fe levels significantly lower than b/+ controls but significantly higher (59)Fe tissue levels in heart, bone marrow, skeletal muscle, kidney, liver, spleen, stomach, and intestines. To study the pharmacokinetics of nonheme iron absorption at the time of weaning, (59)FeCl(3) was administered to 21-day-old b/b and b/+ rats by intragastric gavage. Blood (59)Fe levels measured 5 min to 4 h postgavage were significantly lower in b/b rats, consistent with impaired DMT1 function in intestinal iron absorption. Tissue (59)Fe levels were also lower in b/b rats postgavage. Combined, these data suggest that DMT1 function is not essential for iron assimilation from milk during early development in the rat.     

Single and multiple congenic strains for hydrocephalus in the H-Tx rat

The H-Tx rat has fetal-onset hydrocephalus with a complex mode of inheritance. Previously, quantitative trait locus mapping using a backcross with Fischer F344 rats demonstrated genetic loci significantly linked to hydrocephalus on Chromosomes 10, 11, and 17. Hydrocephalus was preferentially associated with heterozygous alleles on Chrs 10 and 11 and with homozygous alleles on Chr 17. This study aimed to determine the phenotypic contribution of each locus by constructing single and multiple congenic strains. Single congenic rats were constructed using Fischer F344 as the recipient strain and a marker-assisted protocol. The homozygous strains were maintained for eight generations and the brains examined for dilated ventricles indicative for hydrocephalus. No congenic rats had severe (overt) hydrocephalus. A few pups and a significant number of adults had mild disease. The incidence was significantly higher in the C10 and C17 congenic strains than in the nonhydrocephalic F344 strain. Breeding to F344 to make F.H-Tx C10 or C11 rats heterozygous for the hydrocephalus locus failed to produce progeny with severe disease. Both bicongenic and tricongenic rats of different genotype combinations were constructed by crossing congenic rats. None had severe disease but the frequency of mild hydrocephalus in adults was similar to congenic rats and significantly higher than in the F344 strain. Rats with severe hydrocephalus were recovered in low numbers when single congenic or bicongenic rats were crossed with the parental H-Tx strain. It is concluded that the genetic and epigenetic factors contributing to severe hydrocephalus in the H-Tx strain are more complex than originally anticipated.     

F-DIO obesity-prone rat is insulin resistant before obesity onset

We previously created a novel F-DIO rat strain derived by crossing rats selectively bred for the diet-induced obesity (DIO) phenotype with obesity-resistant Fischer F344 rats. The offspring retained the DIO phenotype through 3 backcrosses with F344 rats but also had exaggerated insulin responses to oral glucose before they became obese on a 31% fat high-energy (HE) diet. Here, we demonstrate that chow-fed rats from the subsequent randomly bred progeny required 57% lower glucose infusions to maintain euglycemia during a hyperinsulinemic clamp in association with 45% less insulin-induced hepatic glucose output inhibition and 80% lower insulin-induced glucose uptake than F344 rats. The DIO phenotype and exaggerated insulin response to oral glucose in the nonobese, chow-fed state persisted in the F6 generation. Also, compared with F344 rats, chow-fed F-DIO rats had 68% higher arcuate nucleus proopiomelanocortin mRNA expression which, unlike the increase in F344 rats, was decreased by 26% on HE diet. Further, F-DIO lateral hypothalamic orexin expression was 18% lower than in F344 rats and was increased rather than decreased by HE diet intake. Finally, both maternal obesity and 30% caloric restriction during the third week of gestation produced F-DIO offspring which were heavier and had higher leptin and insulin levels than lean F-DIO dam offspring. Third-gestational week dexamethasone also produced offspring with higher leptin and insulin levels but with lower body weight. Thus F-DIO rats represent a novel and potentially useful model for the study of DIO, insulin resistance, and perinatal factors that influence the development and persistence of obesity.     

Developmental and neurobehavioural toxicity study of arsenic on rats following gestational exposure

To characterize developmental and behavioral alterations induced by arsenic exposure, Albino rats were exposed to arsenic (0, 1.5, 3.0 and 4.5 mg/kg/day/po) from gestation day 8 to till parturition and the offspring were observed over the first 3 postnatal weeks, until they were weaned on post-natal day (PND) 21. Once the pups were delivered (PND0), the treatment was discontinued. All pups were assessed for physical development, reflex development, strength and motor coordination from standard neurobehavioural developmental test batteries beginning on PND1. Gestational administration of arsenic at tested dose levels, showed no significant changes in the day of appearance of eye opening, startle reflex, negative geotaxis and spontaneous alteration performance in comparison to the control group. The number of live fetuses, mean fetal body weight and percentages of resorptions or malformations per litter were not affected by arsenic exposure. No treatment-related malformations or developmental variations were noted at any exposure level, suggesting that arsenic exposure at this dose level did not adversely affect behavioural endpoints of developmental toxicity.     

Alterations in diaphragmatic oxidative and antioxidant enzymes in the senescent Fischer 344 rat.

We investigated age-related changes in antioxidant, glycolytic, beta-oxidation, and tricarboxylic acid cycle enzyme activity in the diaphragm and plantaris muscle of female Fischer 344 rats. Tissue samples from the costal and crural diaphragm and plantaris muscle were obtained from 30 animals in the following age groups: 1) 6 mo old (n = 10), 2) 26 mo old (n = 10), and 3) 30 mo old (n = 10). Aging had no effect (P greater than 0.05) on the activities of citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HADH) in the costal or crural diaphragm. Similarly, no age-related differences existed (P greater than 0.05) in the crural diaphragm in lactate dehydrogenase (LDH) or glutathione peroxidase (GPX) activity. In contrast, the activities of LDH and GPX were significantly (P less than 0.05) higher in the costal diaphragm in the 30- than in the 6-mo old animals. In addition, the ratio of LDH to CS activity increased (P less than 0.05) as a function of age in the costal diaphragm. Conversely, the ratio of CS to GPX activity in the costal diaphragm was lower (P less than 0.05) in the 30- than in the 6-mo old animals. No significant (P greater than 0.05) age-related differences existed in LDH-to-CS or CS-to-GPX activity ratios in the crural diaphragm. Finally, aging resulted in a significant decrease (P less than 0.05) in the activities of LDH, CS, and HADH in the plantaris muscle. These data demonstrate that, unlike many hindlimb locomotor muscles, the oxidative capacity of the Fischer 344 rat diaphragm does not decrease in old age.