Metabolic and hormonal responses to exercise in the anti-obese Lou/C rats.

Objective: Lou/C rats are a substrain of Wistar rats that exhibit a spontaneous low caloric intake and no development of obesity with age. Recently, we reported that Lou/C rats, compared to equally food-restricted Wistar counterparts, show lower resting levels of plasma glucose, epinephrine and liver glycogen. To further explore this metabolic particularity, we used exercise (swimming 60 min) as a situation of high-energy demand, to test the ability of Lou/C rats to maintain euglycemia.

Skeletal muscle HSP72 response to mechanical unloading: influence of endurance training.

Aims: It has been shown that increased contractile activity results in heat shock protein 72 (HSP72) accumulation in various skeletal muscles. By contrast, there is no consensus for muscle HSP72 response to muscle disuse for short duration (5-8 days). On the basis of a greater constitutive HSP72 expression in slow-twitch muscles we tested the hypothesis that mechanical unloading for a longer period (2 weeks) would affect this phenotype to a greater extent.

Stimulation of HSP72 expression following ATP depletion and short-term exercise training in fast-twitch muscle.

Aim: Previous data have reported increases in HSP72 expression in skeletal muscles after endurance training but the physiological and biochemical signals that induce HSP72 accumulation remain largely unknown. In this study, we tested the hypothesis that energy status is a key regulatory event for HSP72 accumulation in skeletal muscles.

Methods: Reduction of high-energy phosphate levels was induced by supplementation with a creatine analogue, beta-guanidinopropionic acid (GPA) for 3 weeks while control rats received distilled water in the same conditions.

Effect of voluntary exercise on H2O2 release by subsarcolemmal and intermyofibrillar mitochondria.

Previous data have demonstrated that, to handle the oxidative stress encountered with training at high intensity, skeletal muscle relies on an increase in mitochondrial biogenesis, a reduced H(2)O(2) production, and an enhancement of antioxidant enzymes. In the present study, we evaluated the influence of voluntary running on mitochondrial O(2) consumption and H(2)O(2) production by intermyofibrillar mitochondria (IFM) and subsarcolemmal mitochondria (SSM) isolated from oxidative muscles in conjunction with the determination of antioxidant capacities. When mitochondria are incubated with succinate as substrate, both maximal (state 3) and resting (state 4) O(2) consumption were significantly lower in SSM than in IFM populations.

Metabolic characteristics and body composition in a model of anti-obese rats (Lou/C).

Objective: The aims of this study were to investigate some features of the metabolic profile and the body composition of male Lou/C rats and to examine whether these characteristics are strictly related to the food-intake reduction.

Research Methods And Procedures: Fourteen-week-old male Lou/C rats were compared with age-matched male Wistar rats fed ad libitum (WAL) and another group of male Wistar rats whose food was chronically restricted (WFR) to the same amount as the Lou/C rats from weeks 3 to 14.

Results: Food intake and body weight were significantly (p < 0.

Skeletal muscle HSP72 level during endurance training: influence of peripheral arterial insufficiency.

Heat shock protein 72 (HSP72), the inducible isoform of the HSP70 family, is synthesized in exercised rat muscles and in the ischaemic heart. To determine the isolated and combined effects of chronic ischaemia and repeated exercise on skeletal muscle HSP72 expression, male Wistar rats were subjected to unilateral occlusion of the iliac artery. Beginning 1 week after ischaemia, half the rats were exercised on a motor-driven treadmill once a day, 5 days/week, the other half were restricted to cage activity.

Differential effects of endurance training and creatine depletion on regional mitochondrial adaptations in rat skeletal muscle.

To examine the combined effects of 2-week endurance training and 3-week feeding with beta-guanidinopropionic acid (GPA) on regional adaptability of skeletal muscle mitochondria, intermyofibrillar mitochondria (IFM) and subsarcolemmal mitochondria (SSM) were isolated from quadriceps muscles of sedentary control, trained control, sedentary GPA-fed and trained GPA-fed rats. Mitochondrial oxidative phosphorylation was assessed polarographically by using pyruvate plus malate, succinate (plus rotenone), and ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) (plus antimycin) as respiratory substrates. Assays of cytochrome c oxidase and F(1)-ATPase activities were also performed.

Gender differentiation of the chemoreflex during growth at high altitude: functional and neurochemical studies.

The effect of chronic hypoxia on gender differences in physiology and neurochemistry of chemosensory pathways was studied in prepubertal and adult rats living at sea level (SL; Lyon, France) or at high altitude (HA; La Paz, Bolivia, 3,600 m). HA adult rats had higher hematocrit (Ht%), Hb concentration, resting ventilatory rate (Ve(100)), and higher tyrosine hydroxylase (TH) activity in carotid bodies (CB) than SL animals. At HA and SL, adult females had lower Ht% (46.

Fluid regulatory hormone response to exercise after coca-induced body fluid shifts.

To determine the effect of coca chewing on heart rate (HR), mean arterial blood pressure (MAP), and plasma volume and their relationship with the hormones regulating cardiovascular and body fluid homeostasis, 16 male volunteers were examined at rest and during 1 h of cycle exercise at approximately 75% of their peak oxygen uptake in two trials separated by 1 mo. One trial was performed after the subjects chewed a sugar-free chewing gum (Coca- trial), whereas the other was done after the subjects chewed 15 g of coca leaves (Coca+), with the order of the Coca- and Coca+ trials being randomized. Blood samples were taken at rest, before (R1) and after 1-h chewing (R2), and during the 5th, 15th, 30th, and 60th min of exercise.

Differential effects of ventilatory stimulation by sex hormones and almitrine on hypoxic erythrocytosis.

In the absence of pulmonary disease, hypoventilation is considered to be the primary cause of Chronic Mountain Sickness, and there is some reason to believe that chronic administration of respiratory analeptics could be useful for treatment of this disease. The present study was intended to define comparatively the influence of two potent ventilatory stimulants, namely a combination of progesterone and estrogen and the pharmacological agent almitrine, on catecholaminergic structures implicated in the chemoreflex pathway and on hypoxia-induced polycythemia. Three groups of young male rats born and living at high altitude (3 600 m) were examined: untreated animals (n = 25), rats given ovarian steroids (progesterone plus 17beta-estradiol, n = 25) or almitrine (n = 25) for 6 weeks until sacrifice.

Influence of gender and endogenous sex steroids on catecholaminergic structures involved in physiological adaptation to hypoxia.

Mechanisms underlying sex-related differences in adaptation to high altitude were investigated by assessing the turnover of dopamine and noradrenaline in structures of the chemoafferent pathway, i.e. carotid body and brainstem noradrenergic cell groups (A1, A5, A6, A2 to which chemosensory fibres project).

Body fluid homeostasis and cardiovascular adjustments during submaximal exercise: influence of chewing coca leaves.

The present study was undertaken to determine the haematological and cardiovascular status, at rest and during prolonged (1h) submaximal exercise (approximately 70% of peak oxygen uptake) in a group (n = 12) of chronic coca users after chewing approximately 50 g of coca leaves. The results were compared to those obtained in a group (n = 12) of nonchewers. At rest, coca chewing was accompanied by a significant increase in heart rate [from 60 (SEM 4) TO 76 (SEM 3) beats.

Lactate and epinephrine during exercise in altitude natives.

We tested the hypothesis that the reported low blood lactate accumulation ([La]) during exercise in altitude-native humans is refractory to hypoxianormoxia transitions by investigating whether acute changes in inspired O2 fraction (FIo2) affect the [La] vs. power output (W) relationship or, alternatively, as reported for lowlanders, whether changes in [La] vs. W on changes in FIo2 are related to changes in blood epinephrine concentration ([Epi]).

Coca chewing for exercise: hormonal and metabolic responses of nonhabitual chewers.

To determine the effects of acute coca use on the hormonal and metabolic responses to exercise, 12 healthy nonhabitual coca users were submitted twice to steady-state exercise (approximately 75% maximal O2 uptake). On one occasion, they were asked to chew 15 g of coca leaves 1 h before exercise, whereas on the other occasion, exercise was performed after 1 h of chewing a sugar-free chewing gum. Plasma epinephrine, norepinephrine, insulin, glucagon, and metabolites (glucose, lactate, glycerol, and free fatty acids) were determined at rest before and after coca chewing and during the 5th, 15th, 30th, and 60th min of exercise.

Aerobic capacity and skeletal muscle properties of normoxic and hypoxic rats in response to training.

The aim of this study was to determine, in the rat, the effects of chronic exposure (7-9 weeks) to normobaric hypoxia (FIO2=0.13, equivalent to 3700 m altitude) on cardiac and skeletal muscle properties, on maximal oxygen uptake (VO2max), and endurance time to exhaustion (ETE). In addition, we evaluated the impact of endurance training (90 min of treadmill running per day, 5 days per week, for 9 weeks) on these parameters.

Effects of coca chewing on hormonal and metabolic responses during prolonged submaximal exercise.

The effects of coca chewing on prolonged submaximal exercise responses were investigated in chronic coca chewers and compared with a group of nonchewers. At rest, coca chewing during a 1-h period was followed by a significant increase in blood glucose, free fatty acid, and norepinephrine concentrations and a significant reduction in insulin plasma level. During prolonged (1-h) submaximal (65-70% peak O2 uptake) exercise, chewers displayed a significantly greater adrenergic activation (as evidenced by a higher level of plasma epinephrine) and an increased use of fat (as evidenced by a lower respiratory exchange ratio).

Effects of coca chewing on metabolic and hormonal changes during graded incremental exercise to maximum.

We examined the effects of 1 h of coca chewing on metabolic and hormonal responses during incremental exercise to exhaustion in traditional coca chewers (C; n = 8), and the results were compared with a group of nonchewers (n = 13). For 1 h, C chewed approximately 12 g of coca leaves that resulted in the apparition of cocaine in blood that reached 72 +/- 9 ng/ml. In resting conditions, even though sympathoadrenergic activity (as assessed by norepinephrine and epinephrine plasma levels) was similar in both groups, C displayed a higher level of plasma free fatty acids.

Hormonal and metabolic adjustments during exercise in hypoxia or normoxia in highland natives.

In sea-level natives, exposure to hypoxia for a few weeks is characterized by an increased dependence on blood glucose and a decreased reliance on lactate for energy metabolism during exercise. These metabolic adjustments have been attributed to behavioral changes in the sympathoadrenergic and pancreatic systems. The aim of this study was to test the hypothesis of a reduced sympathoadrenergic activation and subsequent metabolic changes when high-altitude natives are acutely exposed to normoxia.

Effects of adrenalectomy or RU-486 on rat muscle fibers during hindlimb suspension.

The purpose of this study was to investigate the effects of a glucocorticoid antagonist, RU-486, and of adrenalectomy (ADX) on rat skeletal muscle structural properties after 3, 7, and 14 days of hindlimb suspension (H). After H, a significant loss in muscle weight was observed as early as 3 days in soleus (SOL; -10%) and adductor longus (AL; -14%) muscles. In SOL, after only 7 days, a reduction (-14%) in type I fiber percent distribution occurred, accompanied by an increase (+129%) in intermediate type I fibers.

Exercise training fails to prevent glucocorticoid-induced muscle alterations in young growing rats.

The aim of this study was to determine the impact of chronic treatment for 8 weeks with hydrocortisone acetate (5 mg kg-1 day-1) on skeletal muscles, and to evaluate whether sprint training can prevent glucocorticoid-induced muscle atrophy better than endurance training. Biochemical, histological and contractile properties were employed to determine the influence of this steroid on skeletal musculature, and the results were compared to pair-weight animals to take into account the influence of corticoids on growth rate. It was found that hydrocortisone acetate treatment results in a stunted growth, adrenal atrophy and depressed plasma corticosterone levels.

Soleus muscle alterations in spontaneously hypertensive rats are not dependent on activation of beta 2-adrenergic receptors.

The effects of selective beta 2-adrenergic blockade with ICI 118,551 on the histochemical, biochemical, and contractile properties of slow-twitch soleus muscle from spontaneously hypertensive (SHR) and normotensive (WKY) rats were examined from birth to 8-10 weeks of age. Chronic treatment of normotensive rats with ICI 118,551 caused an impairment in the differentiation of slow type fibers during development but failed to alter the fiber type distribution of hypertensive rats. beta 2-Adrenoreceptor blockade was ineffective in reducing the enhanced glycolytic and oxidative capacities of soleus in hypertensive rats.

Whole body and muscle respiratory capacity with dobutamine and hindlimb suspension.

The effects of repeated injections of dobutamine, a synthetic catecholamine, were studied in control and tail-suspended rats to determine whether this drug could improve the metabolic response to unweighting. Dobutamine prevented the decrease in maximal oxygen uptake (VO2max) induced by hindlimb suspension. Furthermore, VO2max was 12% greater in dobutamine-treated animals than in saline-treated control animals.

Additive effects of training and high-fat diet on energy metabolism during exercise.

This study was conducted to obtain additional information about the adaptations after 12 wk of high-fat diet (HFD) per se or HFD combined with endurance training in the rat using a two [diet: carbohydrate (CHO) or HFD] by two (training: sedentary or trained) by two (condition at death: rested or exercised) factorial design. Adaptation to prolonged HFD increases maximal O2 uptake (VO2max; 13%, P less than 0.05) and submaximal running endurance (+64%, P less than 0.

Exercise endurance and fuel utilization: a reevaluation of the effects of fasting.

The effect of fasting on energy utilization during running or swimming was studied in adult male Wistar rats. Compared with fed rats, fasted animals displayed a decreased contribution of carbohydrates in energy supply, with decreased liver and muscle glycogen contents and decreased rate of glycogen breakdown. This was compensated by an enhanced rate of beta-oxidation.

Effect of almitrine administration on pulmonary arterial pressure in resting and exercising dogs.

In addition to its well-known ventilatory effect, a small rise in pulmonary arterial pressure or pulmonary vascular resistance is occasionally observed with chronic administration of almitrine. In order to test the hypothesis of enhancement of exercise pulmonary vasoconstriction by almitrine, mongrel dogs were studied at rest and during submaximal exercise before and after 4 weeks of chronic ingestion of almitrine (10 mg/kg). It was shown that resting pulmonary arterial pressure (PAP) remained unchanged by almitrine treatment.