Corticotropin-releasing hormone and pituitary-adrenocortical responses in chronically stressed rats

Brain corticotropin-releasing hormone (CRH) concentration and pituitary adreno-cortical responses were examined in chronically stressed rats: body restraint stress (6 h/day) for 4 or 5 weeks. Stressed rats showed a reduction in weight gain. CRH concentration in the median eminence and the rest of the hypothalamus were not different between control and chronically immobilized rats. The anterior pituitary adenocorticotropic hormone (ACTH) concentration was elevated in chronically stressed rats, whereas plasma ACTH and corticosterone levels did not differ from the control values. The median eminence CRH concentration was reduced to the same extent at 5 min after onset of ether exposure (1 min) in chronically immobilized rats and controls. However, plasma ACTH and corticosterone showed greater responses to ether stress in chronically immobilized rats than in control rats. Plasma ACTH and corticosterone responses to exogenous CRH were not different between control and chronically immobilized rats, while the response to arginine vasopressin (AVP) was significantly greater in chronically immobilized rats. These results suggest that chronic stress caused an increase in the ACTH-secreting mechanism and that pituitary hypersensitivity to vasopressin might at least be partly responsible for this.     

Sex differences in the effects of chronic stress and food restriction on body weight gain and brain expression of CRF and relaxin‐3 in rats

This study investigated sex‐specific effects of repeated stress and food restriction on food intake, body weight, corticosterone plasma levels and expression of corticotropin‐releasing factor (CRF) in the hypothalamus and relaxin‐3 in the nucleus incertus (NI). The CRF and relaxin‐3 expression is affected by stress, and these neuropeptides produce opposite effects on feeding (anorexigenic and orexigenic, respectively), but sex‐specific regulation of CRF and relaxin‐3 by chronic stress is not fully understood. Male and female rats were fed ad libitum chow (AC) or ad libitum chow and intermittent palatable liquid Ensure without food restriction (ACE), or combined with repeated food restriction (60% chow, 2 days per week; RCE). Half of the rats were submitted to 1‐h restraint stress once a week. In total, seven weekly cycles were applied. The body weight of the RCE stressed male rats significantly decreased, whereas the body weight of the RCE stressed female rats significantly increased compared with the respective control groups. The stressed female RCE rats considerably overate chow during recovery from stress and food restriction. The RCE female rats showed elevated plasma corticosterone levels and low expression of CRF mRNA in the paraventricular hypothalamic nucleus but not in the medial preoptic area. The NI expression of relaxin‐3 mRNA was significantly higher in the stressed RCE female rats compared with other groups. An increase in the expression of orexigenic relaxin‐3 and misbalanced hypothalamic‐pituitary‐adrenal axis activity may contribute to the overeating and increased body weight seen in chronically stressed and repeatedly food‐restricted female rats .     

Diet‐induced Obesity Delays Cardiovascular Recovery from Stress in Spontaneously Hypertensive Rats

Objective: Blood pressure (BP) and heart rate (HR) responses to stress are significant predictors of cardiovascular morbidity and mortality. Because obesity is a major risk factor for cardiovascular disease, we examined whether diet‐induced obesity alters the BP and HR responses to stress and whether these alterations are associated with augmented cardiovascular morbidity in the rat. Research Methods and Procedures: Adult male spontaneously hypertensive rats were fed either a normal diet or high‐fat diet (HFD) for 12 weeks. At weeks 0 and 12, body weight was measured, and BP and HR were recorded by radiotelemetry throughout three consecutive day and night periods and in response to 30‐minute immobilization stress. At the end of the 12‐week intervention, the rats were sacrificed, and their organs and sera were collected. Results: With the intervention, HFD rats showed a significantly greater increase in body weight (as expected) and circulating leptin and free fatty acid levels compared with normal diet rats. In addition, they showed similar increases in BP and HR elevations during stress but significantly slower BP and HR decreases after stress. These HFD‐induced delays in stress recovery were associated with BP and HR elevations during the night (behaviorally active) period and with augmentations in cardiac mass. Discussion: The results of this study indicate that, in spontaneously hypertensive rats, dietary obesity delays cardiovascular recovery from stress, and, in parallel, it promotes the development of nocturnal hypertension as well as cardiac hypertrophy. This suggests that dietary obesity may significantly potentiate the impact of daily stressful experiences on the cardiovascular system.     

Treatment with low-dose resveratrol reverses cardiac impairment in obese prone but not in obese resistant rats

We hypothesized that a low-dose resveratrol will reverse cardiovascular abnormalities in rats fed a high-fat (HF) diet. Obese prone (OP) and obese resistant (OR) rats were fed an HF diet for 17 weeks; Sprague-Dawley rats fed laboratory chow served as control animals. During the last 5 weeks of study, treatment group received resveratrol daily by oral gavage at a dosage of 2.5 mg/kg body weight. Assessments included echocardiography, blood pressure, adiposity, glycemia, insulinemia, lipidemia, and inflammatory and oxidative stress markers. Body weight and adiposity were significantly higher in OP rats when compared to OR rats. Echocardiographic measurements showed prolonged isovolumic relaxation time in HF-fed OP and OR rats. Treatment with resveratrol significantly improved diastolic function in OP but not in OR rats without affecting adiposity. OP and OR rats had increased blood pressure which remained unchanged with treatment. OP rats had elevated fasting serum glucose and insulin, whereas OR rats had increased serum glucose and normal insulin concentrations. Resveratrol treatment significantly reduced serum glucose while increasing serum insulin in both OP and OR rats. Inflammatory and oxidative stress markers, serum triglycerides and low-density lipoprotein were higher in OP rats, which were significantly reduced with treatment. In conclusion, HF induced cardiac dysfunction in both OP and OR rats. Treatment reversed abnormalities in diastolic heart function associated with HF feeding in OP rats, but not in OR rats. The beneficial effects of resveratrol may be mediated through regression of hyperglycemia, oxidative stress and inflammation.     

Effects of pycnogenol treatment on oxidative stress in streptozotocin-induced diabetic rats

Free radicals and oxidative stress have been implicated in the etiology of diabetes and its complications. This in vivo study has examined whether subacute administration of pycnogenol, a French pine bark extract containing procyanidins that have strong antioxidant potential, alters biomarkers of oxidative stress in normal and diabetic rats. Diabetes was induced in female Sprague-Dawley rats by a single injection of streptozotocin (90 mg/kg body weight, ip), resulting (after 30 days) in subnormal body weight, increased serum glucose concentrations, and an increase in liver weight, liver/body weight ratios, total and glycated hemoglobin, and serum aspartate aminotransferase activity. Normal and diabetic rats were treated with pycnogenol (10 mg/kg body weight/day, ip) for 14 days. Pycnogenol treatment significantly reduced blood glucose concentrations in diabetic rats. Biochemical markers for oxidative stress were assessed in the liver, kidney, and heart. Elevated hepatic catalase activity in diabetic rats was restored to normal levels after pycnogenol treatment. Additionally, diabetic rats treated with pycnogenol had significantly elevated levels of reduced glutathione and glutathione redox enzyme activities. The results demonstrate that pycnogenol alters intracellular antioxidant defense mechanisms in streptozotocin-induced diabetic rats.     

Effect of dietary cholesterol on erythrocyte peroxidant stress in vitro and in vivo

The effect of dietary variation of plasma cholesterol concentrations on the susceptibility of erythrocytes to in vitro and in vivo peroxidant stress was studied in rats. Malonyldialdehyde, produced in vivo (endogenous malonyldialdehyde) or following in vitro exposure of cells to 10 mM H2O2 (H2O2 malonyldialdehyde), was used as a measure of peroxidant stress. After 5 weeks, the plasma cholesterol concentrations in rats receiving 1.2% cholesterol + 0.6% cholic acid in their diet rose to 6-times that of control rats receiving a diet without added cholesterol; at the same time, erythrocyte H2O2 malonyldialdehyde in the cholesterol-fed rats decreased significantly relative to the control rats. During subsequent exposure of both groups to in vivo peroxidant stress with phenylhydrazine in two separate dose trials, erythrocyte peroxidant stress remained significantly lower in the cholesterol-fed rats: at a dose of 100 mumol/100 g body weight, H2O2 malonyldialdehyde was lower; at a dose of 25 mumol/100 g body weight, both endogenous and H2O2 malonyldialdehyde were lower. Erythrocyte membrane cholesterol concentrations were 12% higher in the cholesterol-fed rats than in controls. The effects of in vivo peroxidant stress on plasma cholesterol were also studied. In vivo peroxidant stress at the higher dose of phenylhydrazine produced a decrease in plasma cholesterol concentrations of control rats. The lower dose had no effect on this group and the plasma cholesterol concentrations were unchanged in the cholesterol-fed rats during both treatments. The data suggest that elevated plasma cholesterol concentrations are protective against erythrocyte peroxidant stress. The mechanism of cholesterol's protective effect is probably mediated through elevated membrane cholesterol concentrations.     

Effect of prenatal hypoxia on heat stress-mediated cardioprotection in adult rat heart

Fetal programming has profound effects on cardiovascular function in later adult life. We tested the hypothesis that chronic hypoxic exposure during fetal development downregulates endogenous cardioprotective mechanisms in adult rats. Time-dated pregnant rats were divided between normoxic and hypoxic (10.5% O2 from days 15 to 21 of gestation) groups. The male progeny were studied at 2 mo of age. Rats were subjected to heat stress (42 degrees C for 15 min). After 24 h, hearts were excised and subjected to 30 min of global ischemia and 1 h of reperfusion. Prenatal hypoxia did not change adult rat body weight and heart weight, but significantly increased the cross-sectional area of a left ventricular (LV) myocyte. Heat stress significantly improved postischemic recovery of LV function in normoxic control rats, but not in prenatally hypoxic rats. The infarct size in the LV resulting from ischemia-reperfusion was reduced by the heat stress pretreatment in control rats, but not in prenatally hypoxic rats. In accordance, heat stress significantly increased LV myocardial content of heat shock protein 70 only in normoxic control rats. In addition, there was a significant decrease in the LV myocardial content of the PKC-epsilon isoform in prenatally hypoxic rats compared with control rats. We conclude that prenatal hypoxia causes in utero programming of hsp70 gene in the LV, leading to an inhibition of its response to heat stress and a loss of cardioprotection in later adult life.     

Effect of age and hypoxia on beta-adrenergic receptors in rat heart.

Previous reports suggest that hypoxia downregulates cardiac beta-adrenergic receptors from young rats. Because aging alters response to stress, we hypothesized an age-related alteration in the response to hypoxia. Male Fischer-344 rats, aged 3 and 20 mo, were divided into control and hypoxic groups. The hypoxic rats were exposed to hypobaric hypoxia (0.5 atm) for 3 wk. After hypoxic exposure, body weight decreased, hematocrit increased, right ventricular weight increased, and left ventricular weight decreased in all animals. beta-Adrenergic receptor density declined after hypoxic exposure in the young but not in the older animals, a change that was confined to the left ventricle. beta-Adrenergic receptor density in the right ventricle was significantly lower in the older animals than in the young animals. Plasma catecholamines (norepinephrine, epinephrine) drawn after the animals were killed (stress levels) decreased in young rats and increased in old rats after the exposure to hypoxia. Hypoxia is a useful physiological stress that elucidates age-related changes in cardiac beta-adrenergic receptor and catecholamine regulation that have not previously been described.     

Effect of exposure to stress applied during early ontogenesis on the avoidance reaction in young rats

A study was made of the influence of stress (swinging) applied on the first to the fifth day of life of newborn rats, on acquistion of active unilateral avoidance, passive avoidance of a dark "dangerous" compartment, the relative weight of the brain and absolute increase in the weight of the body at an early age. It was shown that in four-week old rats the stress significantly worsens active avoidance acquisition. In two-month old animals avoidance of a dark "dangerous" compartment, i.e. "passive" avoidance, tested immediately after application of electric current is more pronounced in stressed rats. No difference was found in the relative weight of the brain and the absolute increase in the weight of the body between control and stress groups of the animals.     

Effects of running training on in vitro brown adipose tissue thermogenesis in rats

Brown adipose tissue (BAT) is a major site of nonshivering thermogenesis (NST) during cold acclimation for most mammals. Repetitive nonthermal stress such as immobilization has been shown to enhance the capacity of NST as cold acclimation. In the present study, the effects of running training, another type of nonthermal stress, were investigated on in vitro thermogenesis and the cellularity of interscapular BAT in rats. The rats were subjected to treadmill running for 30 min daily at 30 m/min under 8° inclination for 4–5 weeks. In vitro thermogenesis was then measured in minced tissue blocks incubated in a Krebs-Ringer phosphate buffer containing glucose and albumin at 37° C, using a Clark type oxygen electrode. The trained rats showed less body weight gain during the experiment. The weights of BAT and epididymal white adipose tissue were smaller in the trained rats. Noradrenaline- and glucagon-stimulated oxygen consumption were also significantly smaller in the trained rats. The tissue DNA level was greater in the trained rats, but the DNA content per tissue pad did not significantly differ. The results indicate that running training reduces BAT thermogenesis, possibly as an adaptation to conserve energy substrates for physical work.     

Cardiac hypertrophy and changes in contractile function of cardiomyocyte

To investigate the cellular mechanisms of pressure-overload cardiac hypertrophy transition to heart failure, we observed time course of changes in morphology and contractile function of cardiomyocytes in transverse abdominal aortic constriction (TAC) rats. Since TAC rats suffered higher stress, body weight had a slower growth rate compared with that of synchronous control rats. Therefore, the left ventricular to body weight ratio produced experimental bias to evaluate the degree of cardiac hypertrophy. Length and width of collagenase-isolated cardiomyocyte were directly measured. Length, width and calculated surface area of cardiomyocyte showed a progressive increase in 8-, 16-, and 20-week TAC rats. The increasing rate of surface area in cardiomyocytes was higher at the middle stage of TAC (from the eighth to sixteenth week). Due to the constraint of fibrosis formation, the increasing rate of surface area in cardiomyocytes was slower at the late stage of TAC (from the sixteenth to twentieth week). The sarcomere length of cardiomyocytes was unchanged, whereas sarcomere numbers were significantly increased in 8-, 16-, and 20-week TAC rats. Shortening amplitude of unloaded contraction in single cardiomyocyte was significantly enhanced in 1-week TAC rats, but not altered in 8-week TAC rats compared with that in the synchronous control rats. On the contrary, unloaded shortening amplitude of single cardiomyocyte was significantly reduced in 16- and 20-week TAC rats. The above results suggest that the reduced shortening amplitude may be associated with intrinsic molecular alterations in hypertrophied cardiomyocytes.     

Effect of repeated stress and administration of phenobarbital on the lymphoid tissue and on protein metabolism in the lymphocytes of infant and adult rats

Further study of the response to chronic stress stimulation in the early postnatal phase showed that the i.p. injection of physiological saline (stress stimulation) induced lymphopenia, a 50% decrease in the incorporation of 3H-leucine into isolated lymphocytes and a decrease in the weight of the thymus in 7-day-old male rats. No such changes were observed in adult animals. If repeated doses of phenobarbital were administered to stressed young rats, however, lymphopenia did not occur and the rate of the incorporation of 3H-leucine into isolated lymphocytes was not different from the control value; the protein content of the lymphocytes was significantly raised, however. In adult animals, phenobarbital increased the rate of incorporation of 3H-leucine into the lymphocytes. The repeated administration of phenobarbital reduced the weight of the thymus in both young and adult animals, but a decrease in spleen weight was recorded only in the young animals. A single i.p. injection of ACTH or dexamethasone caused lymphopenia and slowed down the incorporation of 3H-leucine into the lymphocytes of both young and adult animals. The results show that the striking decrease observed in the rate of the liver metabolism of corticosterone in suckling young rats not injured by repeated stress stimulation is accompanied by significant changes in the lymphoid tissue.     

Protective role of Vitamin E pre-treatment on N-nitrosodiethylamine induced oxidative stress in rat liver

Nitrosamine compounds are known hepatic carcinogens. In the metabolism of nitrosamines, such as N-nitrosodiethylamine (NDEA), there is evidence of the formation of reactive oxygen species (ROS) resulting in oxidative stress, which may be one of the factors in the etiology of cancer. The formation of ROS may alter the antioxidant system, while the presence of Vitamin E may counteract NDEA induced oxidative stress. This study was planned to determine whether pre-treatment with Vitamin E (40 mg/kg body weight, i.p., twice a week for 4 weeks) to NDEA induced rats provides protection against oxidative stress in liver caused by the carcinogen. A single necrogenic dose of NDEA (200mg/kg body weight) was administered i.p. to the male albino rats with or without Vitamin E pre-treatment and the animals were sacrificed on Days 7, 14 or 21 after the administration of NDEA. The result showed enhanced levels of hepatic lipid peroxidation (LPO) and conjugated dienes of NDEA treated rats as the indices of oxidative stress, however, Vitamin E pre-treated rats administered NDEA showed decreased LPO and conjugated dienes (Day 21). Superoxide dismutase (SOD) activity in liver was not altered significantly in NDEA treated rats with or without Vitamin E pre-treatment. Catalase (CAT) activity was inhibited with NDEA treatment, however, Vitamin E pre-treatment showed recovery in hepatic CAT activity (Days 14 and 21). Total and Se-glutathione peroxidase (GSH-Px) activities and glutathione-S-transferase (GST) activity in liver increased in NDEA treated rats irrespective of Vitamin E pre-treatment. Glutathione reductase (GSH-R) activity as well as total glutathione (GSH) content in liver decreased in NDEA treated animals, both of which were recovered in Vitamin E pre-treated rats administered NDEA. Activities of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were increased significantly following NDEA treatment to rats with or without Vitamin E pre-treatment. The activities of AST and ALT enzymes were significantly reduced on Days 14 and 21 and ALP activity was reduced on Day 21 in NDEA+Vitamin E treated animals when compared to NDEA treated alone. LDH enzyme activity was normalized on Day 14 in Vitamin E pre-treated animals administered NDEA. However, the AST, ALT and ALP enzyme activities remained high in all treatment groups as compared to control group. Normal control and Vitamin E treated alone rats revealed normal histology of liver. On the other hand, NDEA treated animals showed alterations in normal hepatic histoarchitecture, which comprised of necrosis and vacuolization of the cells. However, the rats treated with Vitamin E+NDEA showed that the liver cells were normal, with very little necrosis (Day 21). This study concludes that the pre-treatment with Vitamin E prior to the administration of NDEA, reduced the degree of oxidative stress, although this vitamin produced only slight changes in the hepatic injury, in a time-dependent manner.     

Resistance factor in emotional stress in the brain of rats

The authors review the results of extraction from the brain of emotional stress-resistant donor rats of fractions containing "factor" that causes the increased resistance to stress in recipient rats predisposed to stress. Brain homogenates of donor rats were subjected to thermal treatment, gel filtration on Sephadex G-15 and lyophilization. The fractions extracted are low-molecular weight, thermostable, resistant to pronase hydrolysis and significantly (P less than 0.05) increase the resistance of recipient rats to stress.     

Effect of the growth hormone-secreting tumor StW5 on pituitary and adrenal gland function in rats

A growth hormone-secreting tumor (StW5 was implanted into male rats and resulted in a tripling of adrenal weight concomitant with a 30% decrement in pituitary weight. Plasma concentrations of corticosterone in tumor-bearing (TB) rats were significantly elevated at rest or after ACTH injections or the stress of either anesthesia. The rise in plasma concentrations of corticosterone was due mainly to the large increment in adrenal size although a significant increase in adrenal responsiveness to ACTH was demonstrated in vitro. In addition, plasma corticosterone concentrations were higher in TB rats despite both a doubling of the blood volume and a 50% increase in liver capacity to metabolize corticosterone. Pituitary ACTH content was significantly lower in TB rats, but these pituitary glands could still release near-normal quantities of ACTH as shown both by in vitro incubations and adrenal corticosterone output following ether stress.     

The effect of chronic food and water restriction on open-field behaviour and serum corticosterone levels in rats

In operant conditioning experiments, two methods are commonly used to motivate laboratory rats to perform designated tasks. The first is restricting food so that rats are forced to lose 20% of body weight within one week, followed by maintenance at 80% of the baseline weight for the remainder of the experiment. The second is restricting access to water to 15 min in each 24 h period. These methods are effective in motivating the animals. There is, however, little information available on the effects on performance in tests of behaviour that are not related to operant conditioning. In addition, it is not clear if these commonly used methods of food and water restriction will lead to physiological stress as indicated by an elevation of serum corticosterone. Male rats were either food-restricted to reduce and maintain their weight at 80% of baseline weight, or were restricted to 15 min access to water every 24 h. Activity in the open field was significantly greater in food-restricted rats than in water-restricted or control rats, but freezing behaviour was similar in all experimental groups. Food-restricted rats had a higher mean serum corticosterone level than water-restricted and control rats 37 days after the start of the experimental period. These data suggested that chronically restricting food and maintenance of body weight at 80% of baseline body weight led to significant behavioural changes and physiological stress. In contrast, water restriction did not lead to changes in behaviour or corticosterone levels. A second experiment was conducted to compare the effects of food restriction to 80% of baseline body weight, as described above, with a less stringent protocol in which test rats were initially reduced to 80% of baseline weight, but were then maintained at 80% of an ad libitum fed control rat's weight. Serum corticosterone levels and adrenal gland weights were measured after the initial week of forced weight loss and after maintenance for 21 days. Forced loss of 20% of body weight in the first week led to significantly increased serum corticosterone levels and adrenal gland weights compared to ad libitum fed controls. Serum corticosterone levels and adrenal gland weights in rats maintained at 80% of their initial body weight for 21 days remained higher than ad libitum fed control rats. However, rats maintained at 80% of an ad libitum fed control rat's weight did not differ from control rats in serum corticosterone levels or adrenal gland weights at the end of the 21-day study period. Adjustment of the feeding regimen in this manner eliminated physiological evidence of chronic stress.     

Toxicological Study of Sodium Selenite on Fetal Development and DNA Fragmentation in Liver Cells of Pregnant Rats

The present study was carried out to evaluate the effects of sodium selenite on fetal development and DNA in liver of rats. Pregnant rats were divided into three groups: control group, group treated orally with 5 μg Se/kg body wt. and group treated orally with 10 μg Se/kg body wt. Dams were treated orally with sodium selenite from day 7 to 19 of gestation. Sodium selenite treatment revealed decrease in maternal body weight, reduction in fetal weight, length and number of viable fetuses, increased number of resorbed fetuses and post-implantation loss at the two doses tested. Fetal skeleton showed signs of developmental delay in skull and limbs of the treated groups. Sodium selenite treatment revealed significant reduction of placental and liver weights in treated dams. Sodium selenite-induced oxidative stress in liver tissue of rats as evidenced by increase in lipid peroxidation and glutathione peroxidase activity, while catalase was significantly decreased. Also, increase in DNA fragmentation, marked reduction of hepatic DNA content, and many histopathological changes in the liver were recorded. The results demonstrated that treatment of pregnant rats with sodium selenite at the toxic dosages chosen showed maternal and fetal toxicity that may be concerned with hepatic oxidative stress accompanied with DNA fragmentation and depletion of total DNA content.     

Differences in response to corticotropin-releasing factor after short- and long-term consumption of a high-fat diet

We previously reported an exaggerated endocrine and weight loss response to stress in rats fed a high-fat (HF) diet for 5 days. Others report blunted stress-induced anxiety in rats made obese on a HF diet. Experiments described here tested whether sensitivity to stress-related peptides was changed in obese and nonobese HF-fed rats. Third ventricle infusion of corticotropin-releasing factor (CRF) in rats made obese on HF diet (40% kcal fat) produced an exaggerated hypophagia, which is thought to be mediated by CRF(2) receptors. Obese rats responded to a lower dose of CRF for a longer time than rats fed a low-fat (LF) diet (12% kcal fat). CRF-induced release of corticosterone, which is thought to be mediated by CRF(1) receptors, was not exaggerated in obese HF-fed rats. In contrast, rats fed HF diet for 5 days showed the same food intake and corticosterone response to CRF as LF-fed rats. CRF mRNA expression in the paraventricular nucleus of the hypothalamus was stimulated by mild stress (ip saline injection and placement in a novel cage) in LF-fed rats but not in rats fed HF diet for 5 days because of a nonsignificant increase in expression in nonstressed HF-fed rats. In addition, nonstressed levels of urocortin (UCN) I mRNA expression in the Edinger-Westphal nucleus were significantly inhibited in HF-fed rats. These data suggest that rats that have become obese on a HF diet show a change in responsiveness to stress peptides, whereas the increased stress response in nonobese HF-fed rats may be associated with changes in basal CRF and UCN I mRNA expression.     

Role of nitric oxide in the induction of apoptosis by smokeless tobacco extract

The suggested role of oxidative stress in the pathogenesis of heart failure is largely based on utilizing left heart failure models. The present study on rats evaluated changes in antioxidants as well as oxidative stress in relation to hemodynamic function subsequent to the right heart failure induced by monocrotaline (50 mg/kg, i.p.). During the post-injection period, monocrotaline (MCT)-treated rats demonstrated a persistent growth depression. Two to three weeks after the injection, MCT-treated rats showed signs of fatigue, peripheral cyanosis and dyspnea. In these rats, right heart hypertrophy was confirmed by a significant increase in right ventricular weight as well as right ventricle to body weight ratio. In MCT-treated rats, there was also a significant increase in right ventricular systolic as well as end diastolic pressures. No change in lung and liver wet/dry weight ratios between MCT-treated and control animals was observed. Based on the hemodynamic data as well as other clinical observations, the functional stage achieved was compensated heart failure. Myocardial antioxidant enzymes, catalase, glutathione peroxidase and superoxide dismutase, in the MCT-treated rats were not different compared to control rats. Vitamin E levels were significantly depressed in the RV and there was no change in retinol levels. There was a significant increase in lipid hydroperoxide concentrations in MCT-treated rats as compared to the control group. These data provide evidence that right heart failure is associated with an increase in oxidative stress.     

Changes in vitamin A status following prolonged immobilization (simulated weightlessness).

A study was conducted to investigate the effects of a simulated weightlessness induced by chronic immobilization on vitamin A status. To simulate the stress condition of weightlessness, rats were suspended for 10 days in a special jacket to which metal chains were attached. Animals received a commercial stock diet. Control rats were pair-fed in reference to the suspended rats. As compared with the control, prolonged immobilization resulted in a decrease in body weight gain and an increase in adrenal weight occurred. In the suspended rats, serum concentrations of retinol and retinol-binding protein (RBP) declined. Hepatic retinyl palmitate content increased, and the hepatic retinol level was decreased. The prolonged immobilization led to significantly reduced retinyl palmitate levels in the testis and lung as well as lowered testicular retinol levels. The results suggest that the stress state induced by prolonged immobilization caused accumulation of hepatic retinyl palmitate, decreasing the serum retinol concentration and retinyl ester content in the extrahepatic tissues.