Effect of magnesium supplementation and training on magnesium tissue distribution in rats

The aim of this work is to study the effect of training and Mg supplementation on body pools of Mg and on Mg tissue distribution. Forty male Wistar rats were divided into four groups (n=10): control group (C); trained group (T); Mg-supplemented group (+Mg); and trained and Mg-supplemented group (+MgT). The Mg supplement (100 ppm of Mg) was given in the drinking water for 21 d. The training consisted of swimming during 60% of maximal swimming time obtained in the first session to exhaustion, during 3 wk (5 d a week). The variables measured were: erythrocytes (RBC), hemoglobin (Hb), hematocrit (Hto), total proteins (TP), and Mg in serum, RBC, liver, muscle, bone, and kidney. There was less Mg in liver, muscle, and erythrocyte in trained animals than in control or supplemented animals (T vs C, +MgT vs C and +MgT vs +Mg) (p < 0.01). Trained antimals (T and +MgT) showed higher Mg kidney rates than the untrained ones (p<0.01). There was less bone Mg in control (C) and in supplemented and trained (+MgT) groups than in trained (T) and in supplemented (+Mg) animals (p<0.01). Serum Mg showed a decreasing concentration profile in the following order: +Mg, +MgT, T, C (p<0.01). We conclude that Mg supplementation improves bone and serum Mg levels, but this does not affect Mg status in soft tissues. Maintained exercise leads to a diminution of Mg in the aforementioned soft tissues that is not noticeable in serum, probably provoked by an increase of renal excretion.     

Status and metabolism of iron in elite sportsmen during a period of professional competition

The aim of this study was to determine the effect of both acute exercise and maintained training during a period of competition (3 mo, at the start of the season) on iron metabolism in sportsmen on a professional volleyball team. Twelve sportsmen volunteered for this study. The exercise test was performed on a mechanically braked Monark cycle ergometer and consisted of a triangular progressive test. Three blood samples were obtained in each test: at rest, just after exercise, and after recovery. The following hematological parameters were determined: red blood count (RBC), hemoglobin (Hb) and hematocrit (Hto), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), total proteins (TP), serum iron (Fe) and total iron-binding capacity (TIBC), ferritin (FER), transferrin (TRF), haptoglobin (HPT), and serum cortisol (COR) concentrations. We have found changes in hematological and biochemical variables related to Fe metabolism during the study. The changes observed could be the result of hemoconcentration processes after exercise and, at least in part, to physical stress and muscular damage. We conclude that athletes, after a period of adaptation, with a good plan of work/recovery series, undergo a biological redistribution on hematological and biochemical parameters concerning Fe metabolism during the training and competition period. Also, daily Fe supplementation could restore and mask the true repercussions of maintained training observed in other sports.     

耐力运动对大鼠骨骼肌ERK1/2活性的影响

目的:探讨耐力运动对大鼠骨骼肌蛋白总量(t-ERK1/2)及磷酸化ERK1/2(p-ERK1/2)及ERK2mRMA表达的影响。方法:SD大鼠随机分为对照组和运动组。运动组分为1h/d和1.5h/d组,共7周,运动结束后24h和48h取材,测定葡萄糖和胰岛素浓度;Westernblot法检测骨骼肌t-ERK1/2、p-ERK1/2蛋白表达;RT-PCR法分析ERK2mRNA表达。结果:与对照组比较,运动组胰岛素浓度降低;各运动组p-ERK1/2升高;1.5h/d-24h和-48h组t-ERK1/2增高;1h/d-24h组与1.5h/d-24h和-48hERK2mRNA表达增高。结论:耐力运动可能通过增加ERK1/2活性,提高大鼠骨骼肌对胰岛素的敏感性。     

Metabolic response of endurance athletes to training with added load

Endurance athletes were divided into experimental (n = 12) and control (n = 12) groups to investigate the effects of extra-load training on energy metabolism during exercise. A vest weighing 9%-10% body weight was worn every day from morning to evening for 4 weeks including every (n = 6) or every other (n = 6) training session. After 4 weeks the control group had a lower blood lactate concentration during submaximal running, whereas the experimental group had significantly higher blood lactate and oxygen uptake (p less than 0.01--p less than 0.05), and a lower 2 mmol lactate threshold (p less than 0.05) and an increased blood lactate concentration after a short running test to exhaustion (p less than 0.05). Those experimental subjects (n = 6) who used the added load during every training session had a lower 2 mmol lactate threshold, improved running time to exhaustion, improved vertical velocity when running up stairs and an increased VO2 during submaximal running after the added load increased anaerobic metabolism in the leg muscle during submaximal and maximal exercise. An increased recruitment and adaptation of the fast twitch muscle fibres is suggested as the principal explanation for the observed changes.     

Effects of Pulse Current on Endurance Exercise and Its Anti-Fatigue Properties in the Hepatic Tissue of Trained Rats

Fatigue is synonymous with a wide spectrum of familiar physiological conditions, from pathology and general health, to sport and physical exercise. Strenuous, prolonged exercise training causes fatigue. Although several studies have investigated the effects of electrical stimulation frequency on muscle fatigue, the effects of percutaneous pulse current stimulation on fatigue in the hepatic tissue of trained rats is still unclear. In order to find an effective strategy to prevent fatigue or enhance recovery, the effects of pulse current on endurance exercise and its anti-fatigue properties in exercised rats were studied. Rats were subjected to one, three or five weeks of swimming exercise training. After exercise training, rats in the treated group received daily applications of pulse current. All rats were sacrificed after one, three or five weeks of swimming exercise, and the major biochemical indexes were measured in serum and liver. The results demonstrate that pulse current could prolong the exhaustion swimming time, as well as decrease serum ALT, AST and LD levels and liver MDA content. It also elevated serum LDH activity, liver SOD activity and glycogen content. Furthermore, pulse current increased the expression of Bcl-2 and decreased the expression of Bax. Taken together, these results show that pulse current can elevate endurance capacity and facilitate recovery from fatigue.     

Effects of acute hypobaric hypoxia and exhaustive exercise on AMP-activated protein kinase phosphorylation in rat skeletal muscle

The present study was aimed to explore the changes of phosphorylated AMP-activated protein kinase (pAMPK) level in skeletal muscle after exposure to acute hypobaric hypoxia and exhaustive exercise. Thirty-two male Sprague-Dawley (SD) rats were randomly divided into sea level and high altitude groups. The rats in high altitude group were submitted to simulated 5 000 m of high altitude in a hypobaric chamber for 24 h, and sea level group was maintained at normal conditions. All the rats were subjected to exhaustive swimming exercise. The exhaustion time was recorded. Before and after the exercise, blood lactate and glycogen content in skeletal muscle were determined; AMPK and pAMPK levels in skeletal muscle were detected by Western blot. The results showed that the exhaustion time was significantly decreased after exposure to high altitude. At the moment of exhaustion, high altitude group had lower blood lactate concentration and higher surplus glycogen content in gastrocnemius compared with sea level group. Exhaustive exercise significantly increased the pAMPK/AMPK ratio in rat skeletal muscles from both sea level and high altitude groups. However, high altitude group showed lower pAMPK/AMPK ratio after exhaustion compared to sea level group. These results suggest that, after exposure to acute hypobaric hypoxia, the decrement in exercise capacity may not be due to running out of glycogen, accumulation of lactate or disturbance in energy status in skeletal muscle.     

Interactive effects of anemia and muscle oxidative capacity on exercise endurance

We used endurance training and acute anemia to assess the interactions among maximal oxygen consumption (VO2max), muscle oxidative capacity, and exercise endurance in rats. Animals were evaluated under four conditions: untrained and endurance-trained with each group subdivided into anemic (animals with reduced hemoglobin concentrations) and control (animals with unchanged hemoglobin concentrations). Anemia was induced by isovolemic plasma exchange transfusion. Hemoglobin concentration and hematocrit were decreased by 38 and 41%, respectively. Whole body VO2max was decreased by 18% by anemia regardless of training condition. Anemia significantly reduced endurance by 78% in untrained rats but only 39% in trained animals. Endurance training resulted in a 10% increase in VO2max, a 75% increase in the distance run to exhaustion, and 35, 45, and 58% increases in skeletal muscle pyruvate-malate, alpha-ketoglutarate, and palmitylcarnitine oxidase activities, respectively. We conclude that endurance is related to the interactive effects of whole body VO2max and muscle oxidative capacities for the following reasons: 1) anemic untrained and trained animals had similar VO2max but trained rats had higher muscle oxidative capacities and greater endurance; 2) regardless of training status, the effect of acute anemia was to decrease VO2max and endurance; and 3) trained anemic rats had lower VO2max but had greater muscle oxidative capacity and greater endurance than untrained controls.     

Exercise improves import of 8-oxoguanine DNA glycosylase into the mitochondrial matrix of skeletal muscle and enhances the relative activity

Exercise has been shown to modify the level/activity of the DNA damage repair enzyme 8-oxoguanine-DNA glycosylase (OGG1) in skeletal muscle. We have studied the impact of regular physical training (8 weeks of swimming) and detraining (8 weeks of rest after an 8-week training session) on the activity of OGG1 in the nucleus and mitochondria as well as its targeting to the mitochondrial matrix in skeletal muscle. Neither exercise training nor detraining altered the overall levels of reactive species; however, mitochondrial levels of carbonylated proteins were decreased in the trained group as assessed by electron spin resonance and biochemical approaches. Importantly, nuclear OGG1 activity was increased by daily exercise training, whereas detraining reversed the up-regulating effect of training. Interestingly, training decreased the outer-membrane-associated mitochondrial OGG1 levels, whereas detraining reversed this effect. These results suggest that exercise training improves OGG1 import into the mitochondrial matrix, thereby increasing OGG1-mediated repair of oxidized guanine bases. Taken together, our data suggest that physical inactivity could impair the mitochondrial targeting of OGG1; however, exercise training increases OGG1 levels/activity in the nucleus and specific activity of OGG1 in mitochondrial compartments, thereby augmenting the repair of oxidized nuclear and mitochondrial DNA bases.     

The effects of swimming and running regimens on skeletal muscle glycogen in the rat.

Endurance capacity and the effects of different post-exercise states on skeletal muscle glycogen have been studied in rats trained by swimming or running and in sedentary controls. Regular endurance exercise resulted in increased skeletal muscle glycogen stores. A greater depletion was observed in trained animals than in non-trained animals after a training bout or exhaustive exercise. While muscle glycogen levels did not reflect a differential training stimulus (running vs swimming), swimming as a measure of exhaustive exercise was deemed invalid because of the ability of trained swimmers to avoid stenuous exercise by an alteration of swimming pattern.     

Chronic and acute exercise do not alter Ca2+ regulatory systems and ectonucleotidase activities in rat heart.

The purpose of this investigation was to examine the effects of chronic and acute exercise on the main components involved in excitation-contraction coupling and relaxation in rat heart. Sixty male Wistar rats were divided into a sedentary (S) and three 12-wk treadmill-trained groups (T-1, moderate intensity; T-2, high intensity; T-3, interval running). After 12-wk, 15 rats from the S group and 15 rats from the T-2 group were subjected to a single treadmill-exercise session until exhaustion before being killed at 0, 24, or 48 h (acute exercise). The remaining animals were killed 48 h after the last standard exercise session (chronic exercise). The efficacy of the training programs was confirmed by an increase in treadmill endurance time and in skeletal muscle citrate synthase activity. None of the exercise programs modified heart weight or cardiac oxidative capacity. [(3)H]PN200-110 and [(3)H]ryanodine binding to cardiac homogenates indicated that the density of L-type and sarcoplasmic reticulum (SR) Ca(2+) channels was the same in S and trained rats. The SR Ca(2+)-ATPase activity was also unmodified. Finally, the activities of the ectoenzymes Mg(2+)-ATPase and 5'-nucleotidase, which are involved in degradation of extracellular nucleotides, were not affected by either of the running programs. After the acute exercise session, no changes were detected in either of the tested parameters in heart homogenates of S and T-2 animals. We conclude that neither treadmill-exercise training for 12 wk nor exhaustive exercise alters the density of Ca(2+) channels involved in excitation-contraction coupling or the SR Ca(2+)-ATPase and the ectonucleotidase activities in rat heart.     

The red blood cells in growing guinea pigs. (Cavia cobaya). II. Communication: erythropoiesis and red blood cells in the postnatal development period

Bone-marrow smears of 175 guinea pigs aged 1-27 days and venous blood samples of 351 animals aged 1-25 days were prepared for cell counting. A significant increase of erythroblasts were found between life day 1 and 2; normoblasts increased in number synchronously with a decrease of erythroblasts after the 5th day. The percentage of the erythroid bone marrow increased from 10 to 14 during the developmental period. Beyond the perinatal period the red blood picture is characterized by the following changes: a decrease of erythrocyte count, hematocrit, hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin; a constant mean corpuscular hemoglobin concentration; an increase of the reticulocyte count. The decrease of the red cell count is compensated by a decreasing oxygen affinity attained by an important increase of 2,3-DPG. Nevertheless, the stimulus for a raising erythropoiesis remains constant which can be shown by the growing percentage of erythroid cells and reticulocytes. The difference between the human postnatal development and that of the guinea pig becomes obvious. Cell counts in dependence of body masses in postnatally growing guinea pigs, veil the perinatal finding of the increase in erythrocytes up to the 5th day and the decrease of the mean corpuscular volume after the 3rd day.     

Phosphorus-31 nuclear magnetic resonance study on the effects of endurance training in rat skeletal muscle

To evaluate changes in muscle energetics following endurance training, we measured phosphorus-31 nuclear magnetic resonance (31P NMR) spectra on rat muscle in vivo before and after training in the same animals. The endurance training lasted for 3 months. The 31P NMR spectra were obtained serially at rest, during exercise by electrical stimulation, and during recovery. Intramuscular phosphocreatine (PCr), inorganic phosphate (P(i)), adenosine 5'-triphosphate (ATP) and pH were determined from the NMR spectra. The ratio of PCr:(PCR + P(i) at rest showed no difference between the trained and control groups even after 3 months of training. During exercise, however, this ratio was significantly higher in the trained group than in the control group. The ratio also recovered more rapidly after exercise in the trained group. The intramuscular pH decreased slightly by approximately 0.1 pH unit during exercise but did not show a significant difference between the groups. These results indicated that endurance training of 3 months duration improved the ATP supply system in the muscle. They also demonstrated that 31P NMR is a potent method for evaluating the effects of training in the same individuals.     

Effect of diazepam treatment on metabolic indices in trained and untrained rats

Exercise training, like diazepam, is commonly employed as a means of reducing anxiety. Both diazepam and exercise training have been shown to modify carbohydrate and lipid metabolism as well as influence calcium metabolism in skeletal muscle. As receptor binding and thereby efficacy of diazepam has been demonstrated to be modulated by the lipid environment of the receptor, and changes in calcium levels can affect a number of intracellular signalling pathways, we sought to determine if the interaction of both chronic diazepam and exercise training would modify selected metabolic indices in an animal model. For this purpose, muscle and liver glycogen, blood glucose and plasma free fatty acids (FFA) were measured in sedentary, exercise trained and exercise trained, acutely exhausted animals. Alterations in lipid and carbohydrate metabolism were observed in all experimental groups. Diazepam treatment alone exerts metabolic consequences, such as elevated muscle glycogen and plasma FFA and depressed blood glucose levels, which are similar to those observed with exercise training. When animals are acutely exercised to exhaustion, however, differences appear, including a reduced rise in plasma FFA, which suggests that long-term diazepam treatment does influence exercise metabolism, possibly as a result of effects on the sympatho-adrenal system.     

Zinc content in selected tissues in streptozotocin-diabetic rats after maximal exercise

The Zn metabolism in experimental diabetic rats after maximal exercise was investigated. Forty male wistar rats were used, weighing 240±10 g at the beginning of this experiment. The animals were assigned to one of four experimental groups (n=10): control at rest (CR), control plus exercise (CE), diabetic at rest (DR), and diabetic plus exercise (DE). Experimental diabetes was produced by a single intraperitoneal injection of streptozotocin (STZ) (60 mg/kg). Thirty days after injection of streptozotocin, the animals of groups CE and DE were forced to acute exercise (swimming) until exhaustion. Glucose, rectal temperature (RT), pH, swimming time (ST), hematocrit (Hct), serum, and tissue (heart, liver, kidney, and muscle) Zn concentrations were measured. The streptozotocin treated animals used in the current experiment were diabetic. Increases in hepatic, renal muscle, and serum levels Zn at rest and after exercise until exhaustion were found in normal and diabetic rats. ST decreased (?180%) in the diabetic rat group. In conclusion, the results of the present study indicate that STZ-induced diabetes was associated with altered tissue Zn concentration, both at rest and after exercise.     

Ultrastructural morphometric studies of myocardial cells of rats after 3 hour autolysis with and without preliminary short term physical exertion

The influence of a period of 3 h of autolysis on the ultrastructure of the heart muscle cells of 2 groups of rats was examined. One group was undergone 5 h of swimming training and the other remains without such training. The results indicate that some ultrastructural changes caused by the exercise are the same even after 3 h of autolysis. On the other hand, swimming training before autolysis affects the process of autolysis.     

Effect of endurance exercise training on muscle glycogen supercompensation in rats

Nakatani, Akira, Dong-Ho Han, Polly A. Hansen, Lorraine A. Nolte, Helen H. Host, Robert C. Hickner, and John O. Holloszy. Effect of endurance exercise training on muscle glycogensupercompensation in rats. J. Appl.Physiol. 82(2): 711-715, 1997.The purpose of this study was to test the hypothesis that the rate and extent ofglycogen supercompensation in skeletal muscle are increased byendurance exercise training. Rats were trained by using a 5-wk-long swimming program in which the duration of swimming was gradually increased to 6 h/day over 3 wk and then maintained at 6 h/day for anadditional 2 wk. Glycogen repletion was measured in trained anduntrained rats after a glycogen-depleting bout of exercise. The ratswere given a rodent chow diet plus 5% sucrose in their drinking waterad libitum during the recovery period. There were remarkabledifferences in both the rates of glycogen accumulation and the glycogenconcentrations attained in the two groups. The concentration ofglycogen in epitrochlearis muscle averaged 13.1 ± 0.9 mg/g wet wtin the untrained group and 31.7 ± 2.7 mg/g in the trained group(P < 0.001) 24 h after the exercise.This difference could not be explained by a training effect on glycogensynthase. The training induced ~50% increases in muscle GLUT-4glucose transporter protein and in hexokinase activity inepitrochlearis muscles. We conclude that endurance exercise trainingresults in increases in both the rate and magnitude of muscle glycogensupercompensation in rats.

     

The size of erythrocyte ghosts

The volume of resealed erythrocyte ghosts formed during hypotonic hemolysis of normal human erythrocytes was measured by means of a continuous mean corpuscular volume analyzer. The final volume of resealed ghosts was 140.6 ± 15.2 fl. Strong correlations exist between the volume of ghosts and the initial mean corpuscular volume and mean corpuscular hemoglobin of the erythrocyte, and between the enlargement ratio and the mean corpuscular volume or mean corpuscular hemoglobin of the erythrocyte.     

Further experimental results concerning the relationship of muscular exercise and adrenal function.

The relationship between muscular work and adrenal function was investigated by using daily swimming exercise in the rat. 1. Adrenal in vitro sensitivity to ACTH was found to have increased after six weeks of swimming training 2. In the development of adaptation the main part was played by muscular exercise itself, since a conditioning of the animals merely to the circumstances of swimming failed to stimulate such adaptive changes as seen in the course of regular physical training. 3. Plasma steroid response to certain stressor agents, such as histamine or acute exhaustion (decrease), respectively to ACTH administration (increase) was similar in ACTH-pretreated and regularly exercised animals. 4. In the 6th to 12th weeks of exercise the trained animals developed a lower plasma steroid content at rest than the controls. This feature was retained even four weeks after the cessation of training sessions. Experimental physical training reduced post-exercise steroidemia in the period of adaptation, that is, after the 6th week. After a pause of 4 weeks, however, the post-exercise steroidemia approached again the control values.     

运动训练和停训对鲈鲤幼鱼游泳能力的影响

为探讨运动训练和停训对鲈鲤Percocypris pingi幼鱼运动能力的影响,将480尾(体质量为2.18g±0.12g,体长为5.33cm±0.09cm)鲈鲤幼鱼随机分为4组(每组120尾):对照组(C)、无氧训练组(An)、4BL·s^-1组(BL为体长)(H)和2BL·s^-1组(L)(H组和L组每天均训练8h),在15℃±2℃条件下持续训练30d后停训。分别在训练前(T0)、训练30d后(T30)、停训20d后(DT20)和停训50d后(DT50)测定鲈鲤幼鱼的临界游泳速度(Ucrit)和1.5Ucrit条件下的耐受时间。结果显示:(1)持续运动训练显著提高了鲈鲤幼鱼的有氧和无氧运动能力,而力竭运动训练只提高了鲈鲤幼鱼的无氧运动能力;(2)停训20d后,L组的Ucrit显著高于An组和C组,An组、H组和C组间的差异无统计学意义,而An组和H组的耐受时间仍显著高于对照组,L组和C组间的差异无统计学意义;(3)停训50d后,实验组和C组间Ucrit和耐受时间的差异均无统计学意义。因此,运动训练显著提高了鲈鲤幼鱼的有氧和无氧运动能力,但不同训练方式的提升效果及其维持时间不同。     

The effect of exercise and zinc supplement on the hematological parameters in rats

This study evaluates the consequences of a session of intensive short-duration exercise and Zn supplementation on different hematological variables. Forty male Wistar rats were divided into four groups (n=10): the first nonsupplemented, maintained at rest (R); the second nonsupplemented, undergoing exercise (E); the third supplemented with Zn, kept at rest (ZnR); and the fourth supplemented with Zn, undergoing exercise (ZnE). Zinc supplements (200 ppm) were given in drinking water. The exercise consisted of a single session of swimming until exhaustion. At rest, RBC, Hb, and Hto fell (p<0.05), whereas red cell indices, MCV, and MCH rose (p<0.05) in +ZnR compared with R; MCHC remained unchanged (ZnR vs R). After exercise, RBC, Hb, and Hto increased significantly in E and in ZnE compared with R and ZnR, respectively. In addition, RBC and Hb were lower (p<0.01) in ZnE compared with E; however, MCV and MCH were higher (p<0.05) in the group ZnE vs E. With respect to white blood cells—leukocytes (WBC), limphocytes (LYMPH), and neutrophiles (NEUT)—no significant differences were observed between groups at rest (ZnR vs R). WBC and LYMPH increased significantly in E with respect to the rest situation (E vs R), but this did not happen in supplemented animals (ZnE vs ZnR). Level of pH decreased after exercise both in E and in ZnE, but the fall was lower in the latter. We believe that a single session of swimming until exhaustion leads to an increase in RBC, Hb, and Hto without causing changes in MCV, MCH, and MCHC. On the other hand, Zn supplementation leads to an increase of MCV and MCH, although they remain within normal levels. Furthermore, this supplementation produces lower metabolic acidoses after exercise that leads to leukocyte stability.