Effects of treadmill running and swimming on plasma and brain vasopressin levels in rats

The influence of treadmill or swimming exercise on resting values of plasma and brain arginine vasopressin (AVP), and plasma sodium, potassium, osmolality and proteins was studied after 5 weeks of training using female Wistar rats. The duration of daily training sessions was progressively increased to reach 6 h/day for swim training (S) and 3 h/day for treadmill running (T). Compared to their untrained controls, treadmill and swim training were respectively associated with: a significant lower body weight; a decreased plasma AVP (36.4% for T and 47.4% for S) and hypothalamic AVP (20% for T and 16% for S); a higher hypophyseal AVP (145% for T and 36.3 for S); a decreased plasma osmolality (6.7% for T and 6.1% for S), sodium (1.2% for both) and potassium (15% for T and 22.4% for S); and no change in protein concentration. For T, rectal temperature increased (38.5 +/- 0.20 to 39.7 +/- 0.5) and for S rectal temperature decreased from 38.6 +/- 0.12 to 37.74 +/- 0.10). The differences observed in AVP contents of the pineal and Harderian glands (enhanced only in the treadmill groups) could be explained by the supposed role of these glands in thermoregulation. Two conclusions could be drawn from this study: there are no parallel changes in the hypothalamo-hypophyseal system (where AVP plays its endocrine role) and the brain (where AVP is a neurotransmitter); plasma changes could be explained by an extracellular fluid expansion with Na and K loss leading to a decrease in AVP secretion.     

Acute cardiorespiratory responses of hypertensive rats to swimming and treadmill exercise

The acute cardiorespiratory responses of spontaneously hypertensive rats (SHR) to swimming and running exercise was investigated because SHR populations are hyperresponsive to external stimuli, of the paucity of existing data, and of the uncertainty on the role of exercise stimuli for training adaptations to occur. Male rats were assigned to one of five groups (n = 5-6/group) and designated as controls (C), inexperienced or naive free swimmers (NFS), experienced free swimmers (FS), experienced weighted swimmers (WS) (attached weights equal to 2% of their body weight) or experienced runners (R) who ran at an intensity of 75% of their VO2max. After 75 min in the water, all groups were acidotic and hypercapnic with the WS experiencing the greatest changes. Heart rate (HR) was increased in all swimmers during the initial 10 min, but declined thereafter, and after 75 min, the HR of WS (348 +/- 1 beats/min) was significantly lower than the C group (416 +/- 22 beats/min). At the same time interval, mean arterial blood pressure (MAP) was decreased in all swimming groups to values lower than the C animals. In addition, an exaggerated diving reflex was frequently noted when the rats were submerged. When the magnitudes of the changes were evaluated in the swimming animals they were directly associated with their submergence times, i.e., during 65-75 min of the swim, NFS, FS, and WS were submerged for 43, 46, and 66% of their total swim time, respectively. In sharp contrast to the swimmers, the runners exhibited increases in HR and MAP with their blood gas measurements being indicative of hyperventilation. We concluded that swimming as an exercise mode for hypertensive rats is best served to study the combined effects of excitement, prolonged submergence, and the consequences of the diving reflex.     

Effect of treadmill exercise on bone mass in female rats.

Increasing peak bone mass at skeletal maturity, minimizing bone loss during middle age and after menopause, and increasing bone mass and preventing falls in advanced age are important measures for preventing osteoporotic fractures in women. Exercise has generally been considered to have a positive influence on bone health. This paper reviews the effects of treadmill exercise on bone in young, adult, ovariectomized, and osteopenic female rats. Treadmill exercise increases cortical and cancellous bone mass of the tibia as a result of increased bone formation and decreased bone resorption in young and adult rats. The increase in lumbar bone mass seems to be more significant when long-term exercise is applied. Treadmill exercise prevents cancellous bone loss at the tibia as a result of suppressed bone resorption in ovariectomized rats, and increases bone mass of the tibia and mechanical strength of the femur, as a result of suppressed bone resorption and increased bone formation in osteopenic rats after ovariectomy. Treadmill exercise transiently decreases the serum calcium level as a result of accumulation of calcium in bone, resulting in an increase in serum 1,25-dihydroxyvitamin D(3) level and a decrease in serum parathyroid hormone level. We conclude that treadmill exercise may be useful to increase bone mass in young and adult rats, prevent bone loss in ovariectomized rats, and increase bone mass and bone strength in osteopenic rats, especially in the long bones at weight-bearing sites. Treadmill exercise may have a positive effect on the skeleton in young, and adult, ovariectomized, and osteopenic female rats.     

Effect of acute exercise on plasma neurotensin levels

Neurotensin (NT) levels were examined in five aerobically untrained females aged 20-36 engaged in acute graded exercise testing. In addition to radioimmunoassay measurements, high pressure liquid chromatography was performed to further characterize plasma NT-like immunoreactivity (NTLI). Epinephrine (E), norepinephrine (NE), and lactate (L) responses were also determined. Exercise testing consisted of one hour of treadmill running subdivided into three 20-minute segments representing 50, 60, and 70%, respectively, of the previously determined maximal aerobic capacity. Mock testing established baseline values for each subject. Three components of NTLI were evaluated: NT(1-13), NT(1-8), and NT(1-11). Resting NT(1-13) concentrations averaged 5.8 +/- 4.2 fmol/ml, while mean NT(1-8) values were 13.0 +/- 5.2 fmol/ml, and NT(1-11) averaged 5.8 +/- 3.2 fmol/ml. Peak exercise values were: for NT(1-13), 5.4 +/- 2.0 fmol/ml, for NT(1-8), 13.5 +/- 2.8 fmol/ml, and for NT(1-11), 5.9 +/- 0.5 fmol/ml. Analysis of variance with repeated measures detected no changes in these levels with exercise. Four-fold increases in E (36 +/- 3 pg/ml to 121 +/- 51 pg/ml), NE (340 +/- 95 pg/ml to 1431 +/- 319 pg/ml), and L (0.8 +/- 0.1 mM to 4.3 +/- 1.7 mM) confirmed the stress of exercise on the body in general, and the sympatho-adrenal system in particular. While other research has associated peripheral NT metabolite elevations with stressful stimuli in laboratory animals, the results of the present study suggest either that NT is not released from the human adrenal medulla during exercise, or that peripheral sampling precludes detection of any increases in NT from the adrenal medulla with currently available radioimmunoassay systems.     

Stress biomarkers in rats submitted to swimming and treadmill running exercises

The objective of the present work was to compare stress biomarkers (serum ACTH and corticosterone hormones) during known intensity swimming and treadmill running exercises performed by rats. Adult Wistar rats (n=41) weighing 320-400 g at the beginning and 420-500 g at the end of the experiment, previously adapted to exercise and with Maximal Lactate Steady State (MLSS) already determined were used. The animals were divided into the following subgroups: (1) sacrificed shortly after session of 25 min of exercise (swimming or treadmill) at the MLSS intensity or (2) sacrificed after exhaustive exercise (swimming or treadmill) at intensity 25% higher than MLSS. For comparison, a control group C was sacrificed at rest. Two-way ANOVA was used to identify differences in the stress parameters (P<0.05). At both exercise intensities serum ACTH concentrations were significantly higher for the swimming group compared to running and control groups, while serum corticosterone concentrations in swimming and running groups were significantly higher than in the control group. The differences were more pronounced at the higher intensity (25% higher than MLSS). The swimming group showed higher concentrations for both hormones in relation to the running group. Only acute swimming exercise induced activity of the hypothalamic-pituitary-adrenal axis responses expected to stress: elevations in the serum ACTH and corticosterone concentrations.     

Effect of treadmill exercise on plasma and urinary cyclic adenosine 3'5'-monophosphate.

The effect of treadmill exercise on plasma and urinary cyclic adenosine 3'5' monophosphate levels (cyclic AMP) was studied in twelve healthy subjects. Plasma cyclic AMP levels were found to be markedly elevated without significant changes in urinary cyclic AMP or cyclic AMP/creatine ratio. Most likely altered plasma glucagon and catecholamine levels were responsible for these changes.     

Effect of long-term swimming exercise on zinc,magnesium, and copper distribution in aged rats

Trace element content of different tissues might be altered by both age and exercise training. We aimed to determine the effects of a 1-yr swimming protocol (60 min/d, 5 day/wk) on tissue levels and the distribution of zinc (Zn), magnesium (Mg), and copper (Cu) in aging rats. Three groups were formed: sedentary and trained old groups and a young control group. Tissue Zn, Mg, and Cu concentrations were measured in the kidney, heart, liver, lungs, and gastrocnemius and soleus muscles. Kidney zinc concentration significantly decreased in the sedentary old group compared to the young control group (p<0.01) and was significantly higher in the trained old group compared to the sedentary old group (p<0.01), whereas Zn levels in the soleus muscle significantly increased in the sedentary old group in comparison to young controls (p<0.05). Tissue Mg concentrations remained unchanged. The sedentary old group exhibited a significant decrease in kidney Cu concentration compared to the young control group (p<0.01). Although kidney Cu levels also decreased in trained old rats in comparison to young controls (p<0.05), they were significantly higher than in sedentary old rats (p<0.01). The decrease in kidney Zn and Cu content as a result of aging was partly prevented by long-term swimming exercise.     

Effects of exercise on plasma lipoprotein levels and endothelium-dependent vasodilatation in young and old rats

Effects of treadmill exercise (1 h.day-1 for 12 weeks) on the mechanical properties of isolated aortae and plasma concentrations of low and high density lipoprotein cholesterols ([LDL-C]pl and [HDL-C]pl, respectively) were investigated in young (16 weeks) and old (98 weeks) rats. With aging, [LDL-C]pl increased and acetylcholine (ACh) elicited greater endothelium-dependent relaxations of the aorta in old rats than in young rats. Also, in all groups of rats tested (young, old, exercised and nonexercised), the increase in the [LDL-C]pl correlated with an increase in the sensitivity of relaxation of the aorta to ACh. On the other hand, a greater [HDL-C]pl was associated with a smaller relaxation response to ACh in young rats only when exercised and nonexercised groups were combined. The increase in [HDL-C]pl with aging, however, did not correlate with the extent of ACh-induced relaxation. Exercise in old rats reduced [LDL-C]pl and the extent of ACh-induced relaxation of the aorta. Therefore, [LDL-C]pl appeared to be closely related to the extent of endothelium-dependent relaxation in response to ACh in the aorta. The [LDL-C]pl also correlated with the gain in mass of the rat. Exercise in old rats reduced the body mass and was accompanied by a decrease in [LDL-C]pl.     

Effects of zinc deficiency and supplementation on malondialdehyde and glutathione levels in blood and tissues of rats performing swimming exercise

The aim of the study was to investigate the effects of zinc deficiency and supplementation on lipid peroxidation and glutathione levels in blood and in some tissues of rats performing swimming exercise. Forty adult male Sprague-Dawley rats were divided into four groups: group 1, zinc-deficient consisted of swimming rats; group 2 consisted of zinc-supplemented swimming rats; groups 3 and 4 were the swimming and nonswimming controls, respectively. The levels of malondialdehyde and glutathione were measured after 4 wk of zinc-deficient or zinc-supplemented diet and 30 min of swimming exercise daily. The erythrocyte glutathione levels of groups 2 and 4 were significantly higher than those of groups 1 and 3 (p<0.01). The plasma malondialdehyde level of group 1 was significantly higher than all other groups. The glutathione levels in liver, kidney, striated muscle, and testes of group 2 were higher than in the other groups (p<0.01) and higher in kidney and striated muscle of group 3 than in groups 1 and 4 (p<0.01). The tissue malondialdehyde levels of striated muscle, liver, kidney, and testes of group 1 were significantly higher than for all other groups (p<0.01). Our findings suggest that both swimming exercise and zinc deficiency result in an increase of lipid peroxidation in tissues and that zinc supplementation prevents these alterations by the activation of the antioxidant system.     

长期游泳运动对大鼠铁状态的影响

目的：观察不同的运动时间对铁状态的影响。方法：大鼠随机分为3、6、12个月的三个游泳运动组和相应安静组;运动期满后观察血液学铁状态指标和器官非血红素铁(NHI)含量和NHI总含量(TNHI)的变化。结果：与安静组相比,三种不同时间长度的运动均诱导一种具有血浆铁浓度降低、血浆转铁蛋白铁饱和度降低而血红蛋白浓度和红细胞比容得到雏持的血液学低铁状态;这种低铁状态伴有肝、脾、心、肾NHI浓度显著降低,但与运动时间无关;肝、脾和肾TNHI变化与其浓度变化方向一致,但心脏没有显著变化;上述器官TNHI随时间增加而增多。结论：尽管运动诱导的低铁状态类似于铁缺乏中期表现,但由于器官NHI重分布和铁贮存并没有进行性降低,因此,长期运动引起的低铁状态可能是机体内铁代谢对运动的适应,不存在所谓“运动性铁缺乏”现象。     

跑台运动和营养补充对大鼠血红素代谢限速酶和珠蛋白mRNA表达与活性水平的影响

目的：研究血红素代谢限速酶和珠蛋白代谢在运动性贫血发生机理中的功能和作用,及营养补充对运动性贫血防治效果的作用机制。方法：本实验对30只雄性Wistar大鼠进行等量随机分为3组（n=10）：对照组（C）、运动组（P）和运动＋营养组（G）。30m／min、0％坡度、每次1min为起始训练方式,前5周和后4周时训练时间的加速度为每次2min,训练频率为每天2次（前两周例外）。11周的跑台运动结束后应用RT-PCR和免疫组织化学的方法测试骨髓每氨基-γ酮戊酸合成酶（ALAs）、铁螯合酶（ferrochelatase）、α-珠蛋白、β-珠蛋白的基因表达和肝脏血红素氧舍酶-1（HO-1）的活性。结果：11周跑台运动可以增加大鼠肝脏HO-1的活性和骨髓β-珠蛋白的基因表达（P〈0．01,P〈0．05）,抗运动性贫血复合剂补充并不能改变大鼠运动后血红素代谢限速酶和珠蛋白基因表达和活性,且运动＋营养组大鼠肝脏HO-1活性水平显著高于对照组（P〈0．01）,即递增负荷跑台运动不能影响大鼠骨髓血红素合成酶和α-珠蛋白的基因表达,但能够影响大鼠肝脏血红素分解酶的活性水平和骨髓β-珠蛋白的基因表达。结论：肝脏HO-1活性水平的升高可能是运动性贫血表现出低Hb、RBC和Hct水平的原因之一。     

Effect of chronic stress on gastric emptying and plasma ghrelin levels in rats

Chronic stress is associated with gastrointestinal functional diseases. Although the pathophysiology seems to be associated with gastrointestinal motility, their mechanisms remain unclear. We investigated gastric emptying and chemical mediators under conditions of continuous stress, which were produced using 8-week-old male Wistar rats kept in a cage filled with water to 2 cm height for 5 days. We examined gastric emptying by the phenol red method and chemical mediators at 4, 8, and 24 h and 3 and 5 days after initiation of stress restraint. Plasma ACTH level was significantly higher in the stress throughout the period of measurement. Continuous stress delayed gastric emptying until 24 h: peak delay was observed at 8 h, whereas gastric emptying was accelerated on days 3 and 5. Plasma noradrenalin level was significantly elevated at every time point until 24 h. Guanethidine pretreatment eliminated the delay in gastric emptying at 8 h. Active ghrelin was significantly increased on days 3 and 5 after peak (at 24 h) plasma total and desacyl ghrelin in the stress group. Number of ghrelin-immunoreactive cells and level of preproghrelin mRNA expression in the gastric body increased in parallel with plasma active ghrelin level. Pretreatment with growth hormone secretagogue receptor antagonist at 5 days partially inhibited the stress-induced acceleration of gastric emptying. Delayed gastric emptying at acute phase of continuous stress was mediated via sympathetic pathway, while acceleration at chronic phase was mediated via increased active ghrelin release from the stomach.