Elder Rats Research Articles

The Effect of Swimming and Resveratrol on Antioxidant Markers and Lipid Peroxidation Index in Liver Tissue

Background Aging is associated with metabolic disorders. Although the beneficial effects of exercise and resveratrol consumption in the health of the elderly has been reported, the combined effect of intermittent swimming and resveratrol consumption on the antioxidant system in liver tissue is not clear yet. Objective This study aims to investigate the combined effect of intermittent swimming and resveratrol consumption on the expression of superoxide dismutases (SOD), glutathione peroxidase (GPx), and Malondialdehyde (MDA) in the liver tissue of older rats. Methods In this experimental study, 32 elder rats were divided into four groups: control, swimming, resveratrol and swimming+resveratrol. The resveratrol (100 mg) dissolved in 1% methylcellulose was administrated daily by gavage. The swimming was performed at three sessions per week. The GPx and SOD expression levels were measured by real-time polymerase chain reaction method, and the MDA level was measured by ELISA method. Results The GPx level in the swimming+resveratrol group were significantly higher than in the control (P=0.001), resveratrol (P=0.04) and swimming (P=0.002) groups. MDA levels in the resveratrol (P=0.001), swimming (P=0.001) and swimming+resveratrol (P=0.001) groups were significantly lower than in the control group; in the swimming+resveratrol group, it was significantly lower than the resveratrol (P=0.001) and swimming (P=0.009) groups. Conclusion It seems that intermittent swimming and resveratrol consumption have favorable effects on improving the antioxidant defense system and lipid peroxidation in liver tissue. Therefore, it is recommended to use intermittent swimming and resveratrol to prevent liver damage in the elderly.

Age-related changes of rats portal vein hemodynamics and morphometry

Introduction. Age-related changes of blood flow parameters and hepatic portal vein wall morphometry are one of the topical and insufficiently investigated issues of liver hemodynamics. The aim was to study changes of portal hemodynamics and to analyze the portal vein wall morphometry of rats at different age periods. Materials and methods. 60 mongrel rats of both sexes weighing 120–350 g were divided into three age groups. The first group included 20 rats aged 1 month, the second – 20 rats aged 6–12 months and the third – 20 rats aged more than 18–24 months. The qualitative and quantitative portal vein hemodynamics parameters were obtained by ultrasound scanners under zoletil-xylazine anesthesia. Morphometric examination of the portal vein was performed. Digital data were processed by methods of variational statistics. Results. The diameter of the portal vein in groups II and III was greater than the corresponding parameter in group I (R = – 0.40 and R = 0.64, respectively). The time-averaged average blood flow rate in the II age group increased by 9.11 % compared to the I group, decreased by 10.43 % in the III group (the differences are statistically unreliable). The volumetric blood flow rate increased moderately in age groups II and III compared to group I (by 13.07 and 11.13 %, respectively; the difference is statistically unreliable). The ratio of the volumetric blood flow rate to the weight of the animal in the II age group increased by 3.85 % compared to the I group, decreased by 11.54 % in the III group (the differences are statistically unreliable). Since the mass of animals significantly increased with age, the portal vein volumetric blood flow of old animals is likely to be decreased. Mature and old rats demonstrated significant decrease of the muscle membrane thickness, the Kernogan index and the width of the collagen layer. Conclusion. Age-related changes of rats portal hemodynamics resulted in a slight reliable increase of portal vein diameter and its cross-sectional area. Linear and volumetric parameters of blood flow were found not to have statistically reliable dependence on the age and weight of animals. Morphometric parameters of the rats portal vein wall were revealed to have pronounced changes in different age groups. The aging of the portal vein wall of elder rats consisted in a significant decrease of the muscle membrane thickness, the Kernogan index and the width of the collagen layer.

The onset of age-related benign prostatic hyperplasia is concomitant with increased serum and prostatic expression of VEGF in rats: Potential role of VEGF as a marker for early prostatic alterations

The onset of age-related benign prostate hyperplasia (BPH) is linked with changes in the expression of specific prostatic chemokines. The aim of this work was to characterize those most relevant changes through the simultaneous analysis of 34 chemokines in both prostatic tissue and serum in rats at different ages with the aim to identify clinically workable parameters for the detection of early prostatic alterations. The study included 28 healthy Sprague-Dawley male rats that were distributed in four groups, 1 month-old (prepuberal; n = 7), 3 months-old (young; n = 7), 6 months-old (mature; n = 7) and 12 months-old (elder; n = 7). Chemokines were analyzed through a commercial mini-array system specially designed for rat tissues. Serum testosterone levels and prostatic histological status were also evaluated. Histological lesions indicative of BPH were detected in three mature rats and in all elder ones. Mini-arrays from prostatic tissue showed that young animals had an overall decreased expression of most of the analyzed chemokines when compared with prepuberal rats, with the exception of agrin, which showed a significant (P < 0.05) increase (100.0 ± 1.3, arbitrary units in prepuberal rats vs.148.2 ± 4.1, arbitrary units in young ones). Older animals showed further specific changes in 4 out 34 analyzed chemokines, namely agrin, platelet-derived growth factor (PDGF), tissue inhibitor of metalloproteinase-1 (TIMP-1) and vascular endothelial growth factor (VEGF). Additionally, elder rats showed the lowest intensity levels of agrin combined with the highest ones for PDGF, TIMP1 and VEGF when compared with all other groups. Finally, a significant increase of serum VEGF was detected in elder, BPH-affected rats when compared with young ones. Results indicated that the onset of both rat puberty and BPH would be related with specific changes in the prostatic expression of chemokines such as VEGF. Otherwise, the observed changes in serum VEGF levels could suggest the future possible utilization of serum VEGF levels to detect early pathological prostatic processes.

Moxibustion may delay the aging process of Wistar rats by regulating intestinal microbiota

As one of the important treatments of health care and anti-aging in traditional Chinese medicine (TCM), moxibustion has been proved to have the effects of scavenging free radicals, anti-oxidation, reducing inflammatory reaction, regulating immunity and so on. Recent studies have shown that intestinal microbiota affect the process of aging. The relationship between aging, moxibustion and intestinal microbiota is still unclear. In this study, we explored the effects of moxibustion at Guanyuan (RN4) acupoint on intestinal microbiota, short-chain fatty acids and immunological characteristics of young and elder female Wistar rats to explore the relationship between aging, moxibustion and intestinal microbiota. Six 12-week-old female Wistar rats were young group (Y), and twelve 36-week-old female Wistar rats were randomly divided into elder group (C) and moxibustion group (M). The rats in M group were received mild moxibustion at Guanyuan (RN4) acupoint, 20 min/d for 40 days. The rats in Y group and C group were not given any therapeutic intervention. The results showed that moxibustion increased the abundance of intestinal probiotics (mainly Lactobacillus) and the level of short chain fatty acids, the microcirculation blood flow around Guanyuan (RN4) acupoint was also significantly improved in elder rats. In addition, the expression of MyD88, MAPK, TRAF6, NF-κB in intestinal tissue was down-regulated, and the levels of inflammatory cytokines in intestinal were decreased.

MORPHOLOGICAL CHARACTERISATION OF THE PANCREAS IN GERONTOGENESIS UNDER EXPERIMENTAL HYPERGLYCAEMIA

The article assessed the development of diabetes mellitus at a reduced dose of alloxan by morphological examination of the pancreas. Middle-aged and elder rats were used in the experiment. The development of hyperglycaemia and its further effects on the pancreas were confirmed during the experiment.

Does circadian rhythm disruption during their early development have lasting effects on cognition of the elder rats?

This study aimed to investigate the changes in learning and memory after chronic circadian disruption followed by a long period of circadian recovery. Eleven adult male spontaneously hypertensive rats were randomly divided into control group, 12-h light/12-h dark circadian disruption group (12L/12D) and 6-h light/6-h dark circadian disruption group (6L/6D). Rats in control group remained under the original 12-h light/12-h dark cycle throughout the experiment; rats in the 12L/12D group were exposed to 12-h light/12-h dark cycle with light-dark order changed every 3 days; rats in the 6L/6D group were exposed to 6-h light/6-h dark cycle. The disruption period continued for 18 weeks. Then after 8 weeks and 32 weeks of circadian re-entrainment, all animals were tested by Morris Water Maze (MWM), respectively, followed by an MRI examination. Rats in the 12L/12D group demonstrated longer escape latency and swim distance in the MWM test than rats in the other two groups (P < 0.05). The MRI results showed volume% reduction and concentration% decrease of brain regions in the two circadian disruptive groups, while the changes were more significant and comprehensive in the 12L/12D group (P < 0.05). Circadian disruption during early life accelerates cognition decline in later life in rats. Frequent light-dark order shift is more harmful.

Effect of Continuous Endurance Training on mRNA Expression of Interferon Gamma and Matrix Metalloproteinase-9 in Male Elder Rats

Background: Aging impairs function of the heart and is associated with mechanical remodeling. This process involves accumulation of collagen and dysfunction in the regulation of activematrixmetalloproteinase. On the other hand, exercise training improves cardiac function and regulates the increase of pro-inflammatory molecules, such as interferon gamma, yet the impact of exercise training on aging has not yet been defined. Objectives: This study examined the effect of continuous endurance training on mRNA expression of interferon gamma (IFN-γ) and matrix metalloproteinase-9 (MMP-9) in male elder rats. Methods: For this purpose, 14 Wistar male rats with age of 24 to 26 months and an average weight of 380 ± 20 g were randomly divided to two groups, including training (n = 7) and control (n = 7). Training groups performed continuous endurance training for six weeks. Matrix metalloproteinase-9 mRNA and interferon (IFN)-γ mRNA expression in heart tissue were measured by real-time polymerase chain reaction. To analyze of the data, the independent t-test was used at a significance level of P &lt; 0.05. Results: The findings of this statistical analysis showed that six weeks of continuous endurance training had a significant effect on MMP-9 mRNA expression (P = 0.001). Also, this training protocol did not have a significant effect on expression of IFN-γ gene (P = 0.628). Conclusions: Continuous endurance training attenuated aging-induced cardiac inflammation of rats. There are numerous questions that remain to be answered to complete the understanding of the moderator effects of exercise on MMP-9 and IFN-γ, as a muscle conformity or indicate an inflammatory condition.

The protective effects of triptolide on age-related bone loss in old male rats

BackgroundPrevious studies have showed that triptolide have a critical role in inhibiting osteoclast formation, bone resorption and attenuating regional osteoporosis. However, the protective role of triptolide on age-related bone loss has not been investigated. In the study, we assessed the effect of triptolide supplementation on bone microstructure and bone remolding in old male rat lumbars. MethodsFifty-two 22-month-old male Sprague-Dawley rats were randomly assigned to either triptolide treatment group or control group. Triptolide (15 μg/kg/d) or normal saline was administered to the rats of assigned group for 8 weeks. Lumbar bone mineral density (BMD) and bone microstructure were analyzed by micro-CT. Fluorochrome labeling of the bones was performed to measure the mineral apposition rate (MAR) and bone formation rate (BFR). Osteoclast number was also measured by TRAP staining. Plasma level of osteocalcin and tartrate-resistant acid phosphatase 5b (Tracp 5b) was also analyzed. ResultsMicro-CT results revealed that triptolide-treated rats had significant higher BMD, bone volume over total volume (BV/TV), trabecular thickness (Tb.Th), bone trabecular number (Tb.N), and lower trabecular separation (Tb.Sp) compared to the control group. Although fluorochrome labeling result showed no significant difference in MAR and BFR between the groups, triptolide decreased osteoclast number in vivo. In addition, a significant higher level of plasma Tracp 5b was observed in the triptolide-treated rats. Furthermore, triptolide also reduced the expression of receptor for activation of NF-κB ligand (RANKL) and increased osteoprotegerin (OPG) expression in the lumbars. ConclusionThese results suggested that triptolide had a protective effect on age-related bone loss at least in part by reducing osteoclast number in elder rats. Therefore, triptolide might be a feasible therapeutic approach for senile osteoporosis.

Influence of aging on experimental gastrointestinal motility in extraction of rat molar teeth

The purpose of the present study was to determine whether different consistency of diet and malocclusion induced by the extraction of molar teeth on the masticatory organs modulated gastric acid secretion, gastric emptying and intestinal transit in young and elder rats. Male Wistar rats (young, 5 weeks; elder, 1.5 years) were used in this experiment, and were divided into 2 groups. Group one (G1) was maintained with solid diet, Group two (G2) with mud diet. Further, the mandibular molar teeth of G2 were extracted. The experimental period was 10 weeks. The effect of aging and malocclusion on the parameters of gastric secretion was examined using pylorus-ligated rats. The gastric emptying rate (GER) and small intestinal transit rate was determined in rats by evans blue from the stomach and charcoal from the small intestinal, respectively. In pylorus-ligated rats, Young-G2 rat of gastric juice volume, acid output and pepsin secretion remarkably showed significant decrease in comparison with Young-G1 group, but there was not significant difference between Elder-G1 and Elder-G2. GER of Young-G2 rat group was 44.2±7.9%, significantly lower than that of Young-G1 rat group (61.6±8.8%, P <0.01), but Elder-G1 rat group were not significantly different than those of rats of Elder-G2 group. In small intestinal transit rates of charcoal meals, G1 and G2 of young were 73.3±9.1 and 55.1±8.6%, respectively, and Elder groups were 61.7±9.8 and 52.6±7.7%, suggesting an insignificant effect on diet. These results suggest that the diet and malocclusion, induced by extraction of mandibular molar teeth of young rat groups, may have a great influence compared to elder rat groups.

Addition of the Immunostimulatory Oligonucleotide IMT504 to a Seasonal Flu Vaccine Increases Hemagglutinin Antibody Titers in Young Adult and Elder Rats, and Expands the Anti-Hemagglutinin Antibody Repertoire

Flu vaccines are partially protective in infants and elder people. New adjuvants such as immunostimulatory oligonucleotides (ODNs) are strong candidates to solve this problem, because a combination with several antigens has demonstrated effectiveness. Here, we report that IMT504, the prototype of a major class of immunostimulatory ODNs, is a potent adjuvant of the influenza vaccine in young adult and elderly rats. Flu vaccines that use virosomes or whole viral particles as antigens were combined with IMT504 and injected in rats. Young adult and elderly animals vaccinated with IMT504-adjuvated preparations reached antibody titers 20-fold and 15-fold higher than controls, respectively. Antibody titers remained high throughout a 120 day-period. Animals injected with the IMT504-adjuvated vaccine showed expansion of the anti-hemagglutinin antibody repertoire and a significant increase in the antibody titer with hemagglutination inhibition capacity when confronted to viral strains included or not in the vaccine. This indicates that the addition of IMT504 in flu vaccines may contribute to the development of significant cross-protective immune response against shifted or drifted flu strains.

Oxidative stress in the kidney of reproductive male rats during aging

Reproduction alters the male physiology. We performed a comprehensive examination of oxidative stress in the kidneys of male rats with (experienced) or without (naïve) reproductive activity during aging. Oxidative stress was assessed by measuring the activity of catalase, glutathione peroxidase, glutathione S-transferase, and superoxide dismutase, and by measuring protein carbonylation, lipid peroxidation, nitrite and nitrate levels, vitamin C levels, and glutathione (total, reduced, and oxidized forms) levels, and metabolism was accessed by aconitase activity in kidney tissue, as well as testosterone and estradiol levels in serum. Reproductively active animals exhibited increased testosterone levels and altered metabolism. Aging affects tissues and organs and contributes to their functional decline. Elderly naïve rats showed high nitrite and nitrate levels. The experienced rats had less damage in elderly ages, probably because they had higher antioxidant amount and antioxidant enzyme activities at earlier ages, which would have avoided oxidative damage seen in naïve group, and because of the metabolism decline. Glutathione increase in naïve elder rats probably was induced for direct protection against oxidative damage and indirect protection by higher glutathione peroxidase and glutathione S-transferase activities. Linear regression shows that lipid peroxidation levels explained vitamin C levels (B standardized value of 0.42), indicating that vitamin C was properly produced or recruited into kidneys to combat lipid peroxidation. Catalase activity reflected the protein carbonylation and lipid peroxidation levels (B standardized values of 0.28 and 0.48). These results add comprehensive data regarding changes in oxidative stress during aging, and suggest an explanation for the costs of reproduction.

Genetic and Epigenetic Interactions between Folate and Aging in Carcinogenesis

Folate is among the most strongly implicated dietary components to convey protection against colon cancer, and diminished folate status is associated with an enhanced risk of colon cancer. Age is also regarded as one of the most important risk factors for colonic carcinogenesis. It is therefore of considerable interest to determine whether the process of aging influences folate metabolism in the colon and whether folate supplementation might prevent the procarcinogenic effects associated with aging. Recent studies in our laboratory demonstrated that the colonic mucosa of elder rats is more susceptible to folate depletion than that of young rats. Depletion of folate results in a shift in the forms of folate in the colon as well as increased uracil incorporation into DNA, a purported mechanism for colonic carcinogenesis. However, modest folate supplementation eliminates evidence of inadequate folate status in the colons of elder rats, suggesting that the relation between age and folate status in the colon might be one mechanism by which aging modulates colorectal cancer risk. Interactions between folate and aging also affect a spectrum of epigenetic and genetic phenomena such as uracil misincorporation, DNA methylation, protein methylation, mitochondrial deletion, and critical gene expression, which could be related to carcinogenesis. Aging and inadequate dietary folate may interact and collectively induce derangements in folate metabolism, thereby provoking subsequent molecular aberrations, which may enhance carcinogenesis. However, folate supplementation appears to reverse these adverse effects of aging, which is potentially of substantial import because the latter is an unmodifiable risk factor.

Effects of ageing and pharmacological hypothyroidism on pituitary–thyroid axis of Dutch-Miranda and Wistar rats

To evaluate the ability of the aged rat pituitary to increase TSH secretion in response to major decreases in serum thyroid hormones, hypothyroidism was induced by methimazole in young and old, male and female, Dutch-Miranda and Wistar rats. Before MMI-treatment there were no differences in serum TSH of young and old rats, but serum T 4 was significantly decreased in aged rats from both genders and strains, while serum T 3 was significantly decreased in aged male rats from both strains, and in old Wistar females. MMI treatment significantly decreased serum T 4 and T 3 in all treated animals, and progressively increased serum TSH in both male and female rats, but the increase was significantly smaller in the elder rats. The pituitary TSH content was higher in Wistar than in Dutch-Miranda rats, of both genders, and was not significantly affected by age. MMI treatment decreased the pituitary TSH in both young and old Dutch-Miranda rats, but in the Wistar strain only the old females had a significant decrease. Our results show that the ability of the pituitary thyrotrophs to increase hormonal secretion in response to decreased levels of thyroid hormones is impaired in the old rat, even when the thyroid hormone levels are dramatically reduced.

Folate supplementation increases genomic DNA methylation in the liver of elder rats

The availability of folate is implicated as a determinant of DNA methylation, a functionally important feature of DNA. Nevertheless, when this phenomenon has been examined in the rodent model, the effect has not always been observed. Several reasons have been postulated for the inconsistency between studies: the rodent is less dependent on folate as a methyl source than man; juvenile animals, which most studies use, are more resistant to folate depletion than old animals; methods to measure genomic DNA methylation might not be sensitive enough to detect differences. We therefore examined the relationship between folate and genomic DNA methylation in an elder rat model with a newly developed method that can measure genomic DNA methylation sensitively and precisely. Thirty-nine 1-year-old rats were divided into three groups and fed a diet containing 0, 4.5 or 18 mumol folate/kg (folate-deplete, -replete and -supplemented groups, respectively). Rats were killed at 8 and 20 weeks. At both time points, mean liver folate concentrations increased incrementally between the folate-deplete, -replete and -supplemented rats (P for trend <0.001) and by 20 weeks hepatic DNA methylation also increased incrementally between the folate-deplete, -replete and -supplemented rats (P for trend=0.025). At both time points folate-supplemented rats had significantly increased levels of DNA methylation compared with folate-deplete rats (P<0.05). There was a strong correlation between hepatic folate concentration and genomic DNA methylation in the liver (r 0.48, P=0.004). In the liver of this animal model, dietary folate over a wide range of intakes modulates genomic DNA methylation.

Specific tau phosphorylation sites in hippocampus correlate with impairment of step-down inhibitory avoidance task in rats

Microtubule associated protein tau is abnormally phosphorylated in Alzheimer's disease (AD) and aggregates as paired helical filaments (PHFs) in neurofibrillary tangles (NFTs), which are one of the pathological signatures of AD and their presence correlates with severity of dementia. Dysfunction of protein phosphatases in the effected neurons is proposed to be a possible causative factor to AD development. We show here that the pattern of tau phosphorylation correlates with the decline of memory retention ability in rat brain. In our study, we have chosen 55 rats of full age to conduct the discrimination between their normal and low ability of memory retention in one-trial step-down test. It was found that among rats that developed the impairment in memory retention in step-down inhibitory avoidance task, tau protein in their hippocampus was hyperphosohorylated at Thr231/Ser235 (M4) sites of tau, and the significantly increased expression of PP-1 and the decreased one of PP-2B were also determined by Western blot and/or immunohistochemistry. It is implicated that: (1) the hyperphosphorylation of tau at M4 sites may be crucial to affect the memory retention of elder rats; (2) PP-1 might participate in the regulation of phosphorylation at Thr231 and Ser235 epitope of tau in vivo, and the up-regulation of PP-1 content could be in relation to tau hyperphosphorylation at Thr231/Ser235 sites of brain tau and the worse memory retention of rats indirectly; and (3) the decline of PP-2B content could induced the hyperphosphorylation of tau at M4 sides in vivo.

Biochemical and Molecular Aberrations in the Rat Colon Due to Folate Depletion Are Age-Specific

Elder adulthood and diminished folate status are each associated with an enhanced risk of colorectal carcinogenesis. We therefore examined whether these two factors are mechanistically related. Weanling male Sprague-Dawley rats (n = 44) and 1-y-old rats (n = 44) were each divided into three groups and fed diets containing 0, 4.5 or 18 micro mol folic acid/kg (deplete, replete and supplemented groups, respectively). Rats were killed at 0, 8 and 20 wk. The folate concentrations, the distribution of the different coenzymatic forms of folate, uracil incorporation into DNA and genomic DNA methylation were measured in the colonic mucosa. Folate-deplete and folate-replete elder rats had 30-45% lower colonic folate concentrations than young rats. Furthermore, 5-methyltetrahydrofolate was uniformly depleted in colons of the elder, folate-deplete rats, whereas this depletion occurred in only a minority of the younger rats. By the end of the experiment, the folate-deplete and folate-replete elder rats had approximately 50% more uracil incorporated into their colonic DNA than the corresponding young groups (P < 0.05). In elder rats, this uracil misincorporation was incremental across the three diet groups (P-test for trend < 0.05), whereas no excess uracil incorporation was observed in young rats. Neither age nor dietary folate affected genomic DNA methylation in the colon. In conclusion, the colon of elder rats is more susceptible to biochemical and molecular consequences of folate depletion than that of young rats. However, folate supplementation is as effective at sustaining adequate colonic folate status in elder rats as it is in the young.

The Na/K-ATPase Regulation By Neurotransmitters In Ontogeny

Activity of the Na/K–ATPase from rat brain synaptic membranes is inhibited by NA (noradrenaline). However, during fractionation of cytozole from nerve endings, two non-homogeneous peaks are found (SF a, 60–100 kD and SF i, ~10 kD), which influence the Na/K–ATPase activity, both directly and SF a NA-dependently. Joint action of NA and synaptic factors (SF a and SF i) on the Na/K-ATPase, represents a sum of four different processes: 1) NA, without synaptic factors, inhibits the Na/K-ATPase; 2) At low SF a concentrations NA-dependent Na/K-ATPase activatory mechanism is evident; 3) At high SF a concentrations NA-independent Na/K-ATPase is activated; 4) The low-molecular SF i protein inhibits the Na/K-ATPase. Regulation of the Na/K-ATPase activity by NA, SF a and SF i, obtained in similar conditions from two weeks old and one year old rats, is different. In older rats SF i is characterized with strong Na/K-ATPase inhibition; in younger rats SF i does not change the Na/K-ATPase activity. The NA- and SF i -dependent inhibition and activation ratio is different in young and elder rats. In two week olds NA/SF i activatory mechanism is stronger, while in one year olds NA-dependent inhibition of the Na/K-ATPase is prevailing. These experimental data indicate that regulation of the Na/K-ATPase activity has an important role in synaptic transmission and that this process has noteworthy, albeit presently unknown, functional importance in integrative activity of the brain.

Influence of maturation on ulcer-development and immunodeficiency induced by activity-stress in rats

Young adult rats housed in the activity-wheel cages and fed only 1 hr daily, have ulcers in the glandular stomach and reveal immunodefeciency. The present study was attempted to investigate how to separate the ulceration and immunodeficiency in order to utilize the activity-stress (A-S) model as an animal model of the human stress ulcer. Six and 10 weeks old rats were used as subjects in this study. They were stressed for 3, 5, or 7 days. In the younger rats, the longer stress exposure caused to deteriorate more both the ulcer and immunodeficiency. The ulceration was found in all of the three stress periods, while the immunodeficiency was recognized in the 5- and 7-day stressed rats. In the elder rats, the ulceration was found in the 5- and 7-day stressed rats, whereas the immunodeficiency was seen only in the 7-day stressed rats. In the free-feeding control rats, relative weights of the thymus and spleen in the elder rats were smaller than those of the younger rats. In the adrenal weight, there was no difference between two age rats. The thymus and spleen of rats exposed to the stress revealed atrophy in both ages. These results suggest that immature rats are more susceptible for the stress than young mature rats, and application of mature rats to the A-S experiment appears to be available in the case of utilizing A-S rats as the stress ulcer model.