Hormonal and metabolic response to physical exercise, fasting and cold exposure in the rat. Effects on ketogenesis in isolated hepatocytes

Four groups of rats were subjected to the following conditions: (1) 48 h fasting, (2) 48 h of 4 degrees C cold exposure, (3) 5 h treadmill running, (4) 48 h fasting with 4 degrees C cold exposure. The groups were compared to fed control rats in order to study hormonal and metabolic responses in blood and tissue samples. Isolated hepatocytes were used to evaluate the rate of ketogenesis. Decreases in liver glycogen and increases in blood free fatty acids (FFA) confirmed that glycogenolysis and lipolysis occur in these situations of metabolic stress. Increases in the glucagon/insulin plasma ratio were also noted. Plasma catecholamine levels were only enhanced after running and after cold exposure. Production of blood ketone bodies was stimulated more by running and by fasting than by cold exposure. The low ketone body production observed after cold exposure seems to be linked to increases liver glycogen levels and decreased FFA availability. Liver cells isolated after cold exposure exhibited higher ketogenesis than these isolated after running. This difference in ketogenic capacity could result both from the longer hormonal stimulation by high glucagon/insulin plasma ratios and from the metabolic state of the liver.     

Effects of plant extract Centella asiatica (Linn.) on cold restraint stress ulcer in rats.

Extract of C. asiatica (Linn.) inhibited significantly gastric ulceration induced by cold and restraint stress (CRS) in Charles-Foster rats, Antiulcer activity of plant extract was compared with famotidine (H2-antagonist) and sodium valproate (anti-epileptic). Plant extract, formotidine and sodium valproate showed a dose dependent reduction of gastric ulceration. Plant extract increased brain GABA level which was also dose dependent. Pretreatment with bicuculline methiodide (specific GABAA-antagonist) at the dose level of 0.5 mg/kg im, reversed the antiulcerogenic activity of both plant extract and sodium valproate. Bicuculline as such did not induce gastric ulceration in normal rat.     

冷拘束应激对大鼠心脏和肝脏HSP70表达及血清中CK、ALT含量的影响

目的通过研究冷拘束应激中大鼠心脏和肝脏组织热休克蛋白（HSP70）表达量以及血清中肌酸激酶（CK）、谷丙转氨酶（ALT）含量的变化,探讨冷拘束应激对心脏和肝脏的影响和差异。方法选取50日龄清洁级大鼠77只,随机分为7组,即0h,0.5h,1.0h,1.5h,2.0h,2.5h,3.0h。采用拘束冷应激法,应激相应时间后,用免疫组织化学方法观察大鼠心脏和肝脏组织HSP70的表达,并检测血清中CK和ALT含量。结果 （1）心脏中HSP70表达量随着应激时间的延长而增加,1.5h组较0h组有明显的增加（P〈0.05）,而2.0h后有极明显的增加（P〈0.01）。（2）肝脏中HSP70表达量随应激时间的延长呈缓慢增加,仅3.0h组有较明显的增加,与0h组、0.5h组及1.0h组比较有显著差异（P〈0.05）。（3）应激开始阶段大鼠血清中的CK含量迅速上升,之后平缓升高;大鼠血清中的ALT含量呈现上升趋势,2.5h以前上升较平缓,2.5h以后急骤升高。结论冷拘束应激可使大鼠心脏中HSP70的表达量和血清中CK含量在较短的时间内显著上升,且随着时间的增加而递增,而肝脏中HSP70的表达量和血清中ALT含量在较短的时间内无明显变化,只有在3.0h时才显著增加,提示心脏对冷拘束应激较敏感,而肝脏对冷拘束应激有较强的耐受性。     

Effect of a 50 Hz electric field on plasma ACTH, glucose, lactate, and pyruvate levels in stressed rats

The effect of extremely low frequency electric field (EF) on stress induced changes of plasma ACTH, glucose, lactate, and pyruvate levels was examined in ovariectomized rats. The rats were exposed to 50 Hz EF (17500 V/m) for 60 min and were restrained for the latter half (30 min) of the EF exposure period. The restraint stress significantly increased the plasma ACTH and glucose levels (P <.05: Student's t test). Restraint induced increase of plasma ACTH and glucose levels tended to be suppressed by exposure to the EF. Meanwhile, the EF exposure also affected plasma lactate level. Thus, the EF exposure significantly decreases plasma lactate levels in the stressed rats (P <.05: Student's t test). Although the precise mechanisms in the restraint dependent alteration in plasma ACTH, glucose, lactate, and pyruvate levels are not fully understood, our results demonstrate that the 50 Hz EF alter both stress responses and energy metabolism in stressed rats.     

The effect of diets on different factors involved in the duration of resistance to low temperature in rats

Cold resistance of male Sprague Dawley rats (300 g) fed a laboratory chow (P) or a semi-purified diet (T4F or H) for 14 days was evaluated by the degree of hypothermia developed under unrestrained conditions at –18°C or under restraint at +6°C or +1°C. Cold tests were started either at 09:00 h, 14:00 h or 23:00 h. Rats fed a semi-purified diet were more resistant to cold than P-fed rats in winter and summer but not in spring or fall. Cold resistance followed a circadian cycle, being very high at 23:00 h, very low at 14:00 h and in between at 09:00 h. The higher resistance to cold of rats on semi-purified diets coincided with a higher liver glycogen reserve throughout the day and a higher production of corticosterone in stressful conditons than in rats on P diet. However, unrelated diurnal cycles of cold resistance and liver glycogen, absence of hypoglycemia and maintenance of a high level of blood corticosterone in hypothermic rats fed P or semi-purified diets indicate that cold resistance is not limited by glycogen availability in liver or glucose and corticosterone in blood respectively. The lower fecal lactobacilli content found in rats fed a semi-purified diet supports the hypothesis that heat producing organs of these animals may have to compete with a smaller bacterial population in their small intestine for essential nutrients than the P-fed rats which could be a factor in their greater degree of cold resistance.NRCC # 17311     

Acute and chronic restraint stress alter the incidence of social conflict in male rats

Stress and elevated stress hormone levels are known to alter cognition, learning, memory, and emotional responses. Three weeks of chronic stress or glucocorticoid exposure is reported to alter neuronal morphology in the hippocampus, the amygdala, and the prefrontal cortex, and to decrease neurogenesis in the dentate gyrus. Here we examine the effects of acute and chronic restraint stress exposure on the incidence of emotional responses throughout a 3-week period among adult rat conspecifics. Our data indicate that acute restraint stress (i.e., a single 6-h exposure) results in a significant reduction in aggressive conflicts among stressed males compared to experimental controls. In contrast, on Days 14 and 21, repeatedly restrained rats exhibited significantly more aggressive behaviors than controls. Blood samples taken 18 h after the last restraint session indicate that plasma concentrations of the stress hormone corticosterone (CORT) in stressed rats were equivalent to those of unstressed rats; however, the number of individually initiated aggressive acts observed positively correlated with plasma CORT measures taken at the end of the study. In contrast to studies of psychosocial stress or intruder paradigms, here we observe spontaneous emotional responses to an uncontrollable stressor in the homecage. This study provides a novel examination of the effects of chronic restraint stress on emotional responses in the home environment among cagemates. These results indicate that acute and chronic restraint stress alter the incidence of aggression, and emphasize the relevance of this model of chronic stress to studies of stress-responsive disorders characterized by aggressive behavior.     

The susceptibility to stress-induced gastric injury of rats exposed to cadmium

In this experimental study, the effect of cadmium on cold and restraint stress-induced gastric lesions has been studied. Rats received 15 μg/mL cadmium-containing water for 30 d, and at the end of this period, they were subjected to cold and restraint stress. Cadmium accumulation in gastric mucosa was associated with increased mucosal lesions, as well as decreased mucin and PGE₂ levels in rats exposed to cadmium. Stress-induced mucosal injury was more pronounced, and the hemoglobin leakage into gastric lumen owing to breakdown in the barrier was 17.30±3.45 μg/mL in control and 35.71±6.18 μg/mL in treated rats. Our data suggest that high cadmium intake facilitates the occurence of stress-induced mucosal lesions by diminishing the mucin content and PGE₂ generation in gastric mucosa.     

Protective effects of nebivolol against cold restraint stress-induced gastric ulcer in rats: role of NO, HO-1, and COX-1,2

Nebivolol, a β(1)-adrenoceptor antagonist, exhibits vasodilatory and anti-oxidative properties that rendering it attractive candidate for protecting against gastric ulcer. The aim of this study therefore is to evaluate the protective effects of nebivolol against cold restraint stress (CRS)-induced gastric ulcer in rats. Rats were restrained, and maintained at 4°C for 3 h. Nebivolol (5 mg/kg, p.o.) was suspended in 0.5% aqueous solution of carboxymethyl cellulose and was administered 30 min before CRS. Nebivolol exhibited gastroprotective effects as evidenced by significant decreases in ulcer index as well as free and total acid output, and pepsin activity in gastric juice in addition to gastric mucosal malondialdehyde concentration, with concomitant increases in gastric juice pH and mucin concentration along with gastric mucosal reduced glutathione and nitric oxide (NO) concentrations compared with CRS rats. Moreover, immunohistochemical analysis demonstrated that nebivolol treatment markedly enhanced heme oxygenase-1 as well as cyclooxygenase-1 and cyclooxygenase-2 expressions. The protective effects of nebivolol were confirmed by gastric histopathological examination. Pretreatment with N(ω)-nitro-L-arginine, a NO synthase inhibitor, partly altered the protection afforded by nebivolol. In conclusion, nebivolol protected rats' gastric mucosa against CRS-induced gastric ulceration possibly through anti-oxidant activity, enhancement of gastric mucosal barrier and reduction in acid secretory parameters.     

Gastric mucosal protection during restraint stress: histologically identifiable gastric mucosal glycosaminoglycan content in albino rats

Male albino rats were subjected to restraint stress for 20 h following 24 h fasting. Tissues from oxyntic and pyloric gland areas of the stomach were processed and stained by the PAS technique to assess the glycosaminoglycan content of the gastric mucosa. The result was compared with that of control rats. A significant reduction in PAS positive materials in both oxyntic and pyloric gland areas of gastric mucosa was observed following 20 h restraint stress. The study indicates the significant role of gastric mucosal glycosaminoglycans in the protection of gastric mucosa against ulcers that develop under restraint stress.     

The role of cadmium in the peroxidative response of kidney to stress

Since the kidney is a main target for cadmium, its accumulation in the kidney tissue by increasing peroxidative damage make the kidney functions vulnerable to stress. For this reason, the effect of cadmium-induced peroxidative damage to kidney responses to stress was investigated in this study. Two-month-old albino rats receiving 15 Μg/mL containing Cd drinking water for 30 d were exposed to restraint and cold stress for 6 h, and their responses were compared with those of unstressed counterparts. Lipid peroxidation was found to be significantly higher in the cortical portion of kidney in cadmium-exposed rats than that of unexposed animals. The mean thiobarbutyric acid reactive substance (TBARS) level rose from 211.6 ± 64.2 to 303.4 ± 46.4 nmol/g protein (p < 0.01). Six hours of cold and restraint stress caused an elevation in the cortical TBARS level in control animals without affecting its level in cadmium-exposed rats. Despite unaltered cortical TBARS, its medullar levels increased significantly in cadmiumexposed rats because of stress. These results suggested that cadmium accumulation in the kidney increases the susceptibility of medulla against peroxidative damage. However, further functional studies are necessary to explain the role of cadmium in the stress-induced deterioration of medullar functions.     

Survial of fasted rats exposed to altitude.

Rats fasted for 48-96h before exposure were shown to have a longer survival time at groups 33,500 ft (1 ft = 0.305 m) simulated altitude than nonfasted controls. Although both become hypothermic at 33500 ft, colonic temperatures of the fasted rats were not sufficiently lower than those of nonfasted animals to explain the difference in survival time. The injection of glucose and insulin before exposure almost completely eliminated the protection afforded by fasting, whereas glucose alone had no effect on survival. It is therefore suggested that an alteration in carbohydrate metabolism, possibly in combination with other starvation-induced changes, allowed fasted rats to survive at 33500 ft until declining body temperature reduced metabolic rate to a level compatible with oxygen supply.     

Determinants of plasma glucose level and diabetic status in a northern Canadian Indian population.

We conducted a cross-sectional survey of 704 Indians aged 20 to 64 years in six remote communities in northern Ontario and Manitoba to determine the factors associated with the fasting plasma glucose and glycosylated hemoglobin levels and diabetic status, defined by past history and current fasting plasma glucose level. Multivariate analyses for the 671 subjects with complete data showed that triglyceride level, age and body mass index (BMI) were significant predictors of the log fasting plasma glucose level and the log glycosylated hemoglobin level; for the latter, waist/hip ratio, history of diabetes mellitus among first-degree relatives and low level of education were additional predictors. Significant risk factors for diabetes as a dichotomous variable included triglyceride level, age, BMI and family history of diabetes. Although energy intake per unit of body weight was lower among subjects with diabetes than those without diabetes, possibly reflecting the lower physical activity level of diabetic subjects, the former consumed significantly more "calorie-adjusted" protein and less carbohydrate than the latter. The findings are consistent with studies in other populations. Further study is needed to determine the natural history of diabetes and its metabolic consequences and to assess the effect of dietary alteration and promotion of physical activity on the incidence of the disease.     

The effect of cocaine on gastric mucosal PGE(2), LTC(4) and ulcerations

The association between cocaine use and acute gastroduodenal perforation is known. The effect of cocaine and stress on gastric mucosal ulceration and the levels of prostaglandin E(2) (PGE(2)) and leukotriene C(4) (LTC(4)) was studied in 40 Sprague-Dawley rats. Controls received intraperitoneal (i.p.) saline, ten received i.p. cocaine (35 mg/kg), ten were stressed by the cold restraint method, and ten had i.p. cocaine and stress. Cocaine alone did not induce ulceration, but decreased PGE(2) levels. Stress alone caused ulceration, but was not associated with a change in either PGE(2) or LTC(4) levels. When combined with stress, however, cocaine caused a three-fold increase in ulceration and a significant increase in PGE(2) and LTC(4) levels. Stress may predispose the cocaine addict to loss of gastroduodenal mucosal integrity, which is related to an imbalance of PGE(2) and LTC(4) synthesis.     

Stress-responsive hypothalamic-nucleus accumbens regulation may vary depending on stressors

This study was conducted to determine if the stress-responsive hypothalamic-nucleus accumbens (NAc) regulation is a stressor specific event. Male SD rats were subjected to restraint or cold stress for 2 h, and then mRNA expression of corticotropin-releasing hormone (CRH) in the hypothalamic paraventricular nucleus (PVN) was examined by in situ hybridization and the plasma corticosterone levels by radioimmunoassay. Neuronal activations in the PVN and the NAc were examined by c-Fos immunohistochemistry and the brain GABA contents by HPLC. Both restraint and cold stresses increased c-Fos expression in the PVN and the plasma corticosterone; however, CRH expression in PVN was increased only by restraint, but not by cold, stress. Restraint stress significantly increased the NAc neuronal activation, but cold stress failed to do so. Restraint stress increased the NAc-GABA contents and cold stress did the hypothalamic GABA. Results suggest that the HPA axis regulation responding to restraint stress, but not cold stress, may involve the NAc neuronal activation in relation with GABAergic neurotransmission. Additionally, CRH expression in the PVN may not play a major role in the elevation of plasma corticosterone responding to cold stress.     

Antihyperglycemic, antistress and nootropic activity of roots of Rubia cordifolia Linn

Effect of alcoholic extract of roots of Rubia cordifolia was studied on elevated blood glucose level in alloxan treated animals. The extract reduced the blood sugar level raised by alloxan. Effect of alcoholic extract was also investigated on cold restraint induced stress and on scopolamine-induced memory impairment. Alcoholic extract enhanced brain gamma-amino-n-butyric acid (GABA) levels and decreased brain dopamine and plasma corticosterone levels. Acidity and ulcers caused due to cold restraint stress were inhibited by alcoholic extract. Animals treated with alcoholic extract spent more time in open arm in elevated plus maze model. It also antagonized scopolamine induced learning and memory impairment. Baclofen induced catatonia was potentiated by alcoholic extract.     

Effect of two distinct stressors on gene expression of the type 1 IP3 receptors

Inositol 1,4,5-trisphosphate (IP3) is one of the second messengers, which triggers calcium release from intracellular pools via IP3 receptors. Previously we have shown that single immobilization stress increased gene expression of both, the type 1 and type 2 IP3 receptors (IP3R1 and IP3R2, respectively). In this study we evaluated whether long-term exposure to softer stressor (cold exposure to 4 degrees C) can affect the response to single immobilization stress. We examined modulation of the type 1 IP3 receptor gene expression by each stressor separately, and then in their combination. Rats were immobilized for 30 min and 120 min and were decapitated immediately or 3 h after immobilization. Cold stress was performed by exposure of animals to 4 degrees C temperature for 1, 7 and 28 days. To determine the effect of both stressors in combination, animals exposed to cold for 28 days were afterwards exposed to immobilization for 120 min and decapitated 3 h after the end of stressful stimulus. Our results verify that single immobilization increases the IP3R1 gene expression in left atria of rat heart, while cold stress elevates the level of gene expression only after the exposure to cold for 7 days. The exposure to cold for 28 days did not increase the gene expression of the type 1 IP3 receptor compared to control. Application of both stressors (28 days of cold exposure followed by 120 min of immobilization with subsequent 3 h rest) showed the tendency of increased IP3R1 gene expression compared to absolute, nonstressed control, but level of the type 1 IP3 receptor mRNA was significantly lower compared to mRNA levels of solely immobilized animals. Thus, cold exposure affects the response of the gene expression of the type 1 IP3 receptor to immobilization stress.     

Effect of nutritional status on insulin sensitivity in vivo and tissue enzyme activities in the rat.

The hyperinsulinaemic-glucose-clamp technique, in combination with measurement of glucose turnover in conscious unrestrained rats, was used to assess the effects of nutritional status on insulin sensitivity in vivo and glucose metabolism. Liver, heart and quadriceps skeletal-muscle glycogen content and activities of pyruvate dehydrogenase (PDH) and glycogen synthase were measured both basally and at the end of a 2.5 h glucose clamp (insulin 85 munits/h) in rats 6, 24 and 48 h after food withdrawal. Clamp glucose requirement and glucose turnover were unchanged by fasting. Activation of glycogen synthase and glycogen deposition in liver and skeletal muscle during the clamps were also not impaired in rats after a prolonged fast. By contrast with skeletal muscle, activation of cardiac-muscle glycogen synthase and glycogen deposition during the clamps were markedly impaired by 24 h of fasting and were undetectable at 48 h. Skeletal-muscle PDH activity fell with more prolonged fasting (6 h, 15.3 +/- 3.4%; 24 h, 4.7 +/- 0.7%; 48 h, 4.3 +/- 0.6% active; P less than 0.005), but at 24 and 48 h was stimulated by the clamp to values unchanged by the duration of fasting. Stimulation of cardiac PDH activity by the clamp was, however, impaired in rats fasted for 24 or 48 h. Basal hepatic PDH did not change significantly with fasting (6 h, 5.3 +/- 1.1%; 24 h, 4.6 +/- 0.7%; 48 h, 3.9 +/- 0.5%), and, although it could be partly restored at 24 h, very little stimulation occurred at 48 h. Hepatic pyruvate kinase and acetyl-CoA carboxylase activity were both stimulated by the clamps, and this was not impaired with more prolonged fasting. During the glucose clamps, blood concentrations of lactate, pyruvate and alanine were increased to a greater extent in rats fasted for 24 and 48 h than in rats studied 6 h after food withdrawal. The findings suggest that, although sensitivity to insulin of whole-body glucose disposal is unchanged with fasting, there may be qualitative differences in the metabolism of glucose.     

Antioxidant enzymes activities and bilirubin level in adult rat treated with lead

Lead toxicity is closely related to its accumulation in several tissues and its interference with bioelements, whose role is critical for several biological processes. Recently, oxidative stress has been proposed as a possible mechanism involved in lead toxicity. This study was carried out to investigate the effect of dose-dependent lead exposure on haematological and oxidative stress parameters. Adult male 'Wistar' rats (150-200 g) were divided into three groups: group [Pb 5] and group [Pb 15] received respectively 5 mg Pb(2+) (n=16) and 15 mg Pb(2+)/kg b.w. (n=16) as lead acetate solution i.p. for a period of seven days. Group [T] (n= 16) served as control and received 15 mg Na(+)/kg b.w. as sodium acetate solution i.p. for the same period. All animals were sacrificed 24 h after the last injection. Blood superoxide dismutase (SOD) and blood glutathione peroxidase (GPx) activities and plasma bilirubin level were measured. Liver was quickly excised for the estimation of alteration in lipid peroxidation indices (MDA). Lead exposure induces, in both treated groups, a marked decline in haematocrit and haemoglobin levels (p<0.01) when compared to control. The results show also a significant decrease (p<0.01) in SOD activity, but only in group [Pb 15]. SOD activity did not decrease in group [Pb 5] in comparison with control (p>0.05). However, lead exposure caused a light increase in GPx activity in group [Pb 15], which remains non-significant (p>0.05) compared to control. Group [Pb 5] did not record significant changes in the activity of GPx. Lead exposure for a period of seven days resulted in a significant (p<0.05) increase in bilirubin level in group [Pb 15] compared to control. The bilirubin level from rats of group [Pb 5] did not reach a statistical significance. Changes in liver MDA content in lead-exposed rats from [Pb 5] and [Pb 15] groups did not reach a statistical (p<0.05) significance. It is concluded that lead induces oxidative stress in a dose-dependent manner. No dose-dependent response was observed in blood GPx activity and liver MDA content. These results could be due to the short duration of the treatment.     

Effect of misoprostol in preventing stress-induced intestinal fluid secretion in rats

Psychological stress may alter gastrointestinal function by central nervous system controlled alteration of local intestinal mediators. Prostaglandins have been shown to prevent epithelial damage to various noxious stimuli. The purpose of this study was to determine (a) if wrap restraint stress altered in vivo intestinal fluid absorption in rats, and (b) if the prostaglandin E1 analogue, misoprostol, could correct observed fluid malabsorption. In vivo loop studies demonstrated net fluid secretion in the ileum and colon of cold wrap restraint stressed rats. In cold wrap restraint stressed rats, misoprostol reversed net secretion to absorption, but it had no effect on fluid absorption in controls. Mild wrap restraint stress did not alter in vivo fluid absorption. We conclude that cold wrap restraint stress is accompanied by net intestinal fluid secretion that can be effectively reversed with misoprostol.     

Physiological changes in rats exposed to cold/restraint stress.

An investigation was made into the effects of cold/restraint stress in rats on renal function, plasma constituents, blood count and endocrine function. Cold/restraint caused an increased volume of urine output, with increased K⁺ and urea excretion, and decreased Na⁺ and Cl^? excretion. There was a fall in plasma glucose, and a rise in plasma urea. A marked leucopenia was found, and the blood pH was significantly lowered. Cold/restraint was also found to cause marked increases in corticosterone and thyroxine levels, and a fall in the insulin level.