Resistance exercise and plasma beta-endorphin/beta-lipotrophin immunoreactivity

Serum cortisol and plasma beta-endorphin/beta-lipotrophic hormone (LPH) immunoreactivity were measured in five males before and after endurance exercise (treadmill) and burst activity resistance exercise (weight lifting). Mean beta-endorphin/beta-LPH immunoactivity increased significantly following treadmill testing (p < .05) and weight training (p < .06). Post-exercise hormonal values were similar for the two activities. The hormonal changes previously reported with endurance activities also occur with burst activity exercise.     

Correlation between beta-endorphin/beta-lipotropin-immunoreactivity and cortisol plasma concentrations

Plasma Cortisol and Beta-Endorphin/Beta-Lipotropin-immunoreactivity concentrations were measured in 51 healthy aged subjects. A direct correlation was found between the plasma concentrations of the two hormones. The data suggest that beta-endorphin/beta-lipotropin is not only released during stress but also in resting conditions.     

Effects of beta-endorphin fragments on plasma levels of vasopressin

Plasma vasopressin levels are significantly decreased after intracerebroventricular (icv) administration of β-endorphin (βE), but not of des-tyrosine βE (DTβE). The βE induced decrease of vasopressin levels, which occurs in normal as well as in water deprivated rats, can partially be blocked by naltrexone. γ-Endorphin (γE), α-endorphin (αE), DTγE and DTαE did not affect basal levels of vasopressin, but γE and DTγE further increased the elevated vasopressin levels in water deprivated rats. Naltrexone antagonized this increase following γE administration, but not that induced by DTγE. The results suggest that the effects of βE and its fragments on plasma vasopressin levels are mediated by multiple opiate and non-opiate receptor systems.     

Effect of heavy-resistance exercise training on muscle fiber composition in young rats

The purpose of this investigation was to determine whether heavy-resistance exercise training alters the skeletal muscle fiber composition of young rats. Ten male Long Evans rats (3 wk old) were trained to lift progressively heavier weights, which were secured to the rats' tails, while they ascended a 40-cm 90 degree mesh incline 20 times/day 5 days/wk for a food reward. After 8 wk of training, they lifted 406 +/- 19 (SD) g in addition to their body weight (261 +/- 9 g). Compared with 10 sedentary pair-fed rats, no hypertrophy of forelimb muscles (biceps brachii and brachialis) was observed, but rectus femoris wet and dry weights were greater (P less than 0.01) in the trained group. In the deep region of the rectus femoris, type I fiber area was similar between groups, but the trained rats had both a lower (P less than 0.05) percentage of type I fibers and a smaller (P less than 0.05) portion of the total area occupied by type I fibers. The percentage of type IIb fibers in the deep region of the rectus femoris was also similar between groups, but the portion of the deep area composed of type IIb fibers was greater (P less than 0.05) in the trained rats. In the superficial region of the rectus femoris, the trained rats' type IIb fibers were larger (P less than 0.01) and occupied a greater (P less than 0.05) portion of the superficial muscle area.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic response of different high-intensity aerobic interval exercise protocols

ABSTRACT: Gosselin, LE, Kozlowski, KF, DeVinney-Boymel, L, and Hambridge, C. Metabolic response of different high-intensity aerobic interval exercise protocols. J Strength Cond Res 26(10): 2866-2871, 2012-Although high-intensity sprint interval training (SIT) employing the Wingate protocol results in significant physiological adaptations, it is conducted at supramaximal intensity and is potentially unsafe for sedentary middle-aged adults. We therefore evaluated the metabolic and cardiovascular response in healthy young individuals performing 4 high-intensity (～90% V[Combining Dot Above]O2max) aerobic interval training (HIT) protocols with similar total work output but different work-to-rest ratio. Eight young physically active subjects participated in 5 different bouts of exercise over a 3-week period. Protocol 1 consisted of 20-minute continuous exercise at approximately 70% of V[Combining Dot Above]O2max, whereas protocols 2-5 were interval based with a work-active rest duration (in seconds) of 30/30, 60/30, 90/30, and 60/60, respectively. Each interval protocol resulted in approximately 10 minutes of exercise at a workload corresponding to approximately 90% V[Combining Dot Above]O2max, but differed in the total rest duration. The 90/30 HIT protocol resulted in the highest V[Combining Dot Above]O2, HR, rating of perceived exertion, and blood lactate, whereas the 30/30 protocol resulted in the lowest of these parameters. The total caloric energy expenditure was lowest in the 90/30 and 60/30 protocols (～150 kcal), whereas the other 3 protocols did not differ (～195 kcal) from one another. The immediate postexercise blood pressure response was similar across all the protocols. These finding indicate that HIT performed at approximately 90% of V[Combining Dot Above]O2max is no more physiologically taxing than is steady-state exercise conducted at 70% V[Combining Dot Above]O2max, but the response during HIT is influenced by the work-to-rest ratio. This interval protocol may be used as an alternative approach to steady-state exercise training but with less time commitment.     

Effects of cocaine on plasma catecholamine and muscle glycogen concentrations during exercise in the rat

This study was designed to test the hypothesis that cocaine (C) alters the normal physiological responses to exercise. Male rats were injected with saline (S) or C (12.5 mg/kg) either intravenously (iv) or intraperitoneally (ip). After injection the animals were allowed to rest for 30 min or were run on the treadmill (26 m/min, 10% grade). At rest plasma epinephrine values were 245 +/- 24 pg/ml in the S group and 411 +/- 43 (ip) and 612 +/- 41 (iv) pg/ml in the C groups (P less than 0.05 between S and C). During exercise plasma epinephrine levels were 615 +/- 32 pg/ml in S and 1,316 +/- 58 (ip) and 1,208 +/- 37 (iv) pg/ml in the C groups (P less than 0.05 between S and C). Similar results were obtained for norepinephrine. Glycogen content in the white vastus lateralis muscle was reduced to 31 +/- 2 mumol/g in S after exercise, but after C and exercise the values were 12 +/- 4 (ip) and 16 +/- 3 (iv) mumol/g (P less than 0.05 between S and C). There was no effect of the drug on this parameter at rest. Blood lactate rose to 4.8 +/- 1.0 (ip) and 5.8 +/- 1.3 (iv) mM in the C groups but to only 3.0 +/- 0.2 in the S group after exercise (P less than 0.05 between S and C). These results show that C and exercise combined exert a more dramatic effect on plasma catecholamine, muscle glycogen, and blood lactate concentrations than do C and exercise alone. They provide further insight into explaining the adverse effects of C on exercise endurance observed previously (Bracken et al., J. Appl. Physiol. 66: 377-383, 1989).     

Relationship between plasma concentrations of immunoreactive beta-endorphin and food intake in rats

Periods of increased food intake in male rats were characterized by significant elevations in the plasma concentrations of immunoreactive beta-endorphin (beta-ep). Administration of 2-deoxy-D-glucose (400 mg/kg) produced rapid and concurrent increases in both food intake and plasma beta-ep. Administration of insulin (10 units/kg) produced large delayed increases in food intake but only modest delayed increases in plasma beta-ep. Spontaneous nocturnal feeding was associated with increased plasma beta-ep. Increases in daytime food intake in rats subjected to 24 hr of food deprivation were also characterized by elevated plasma beta-ep. In all cases examined, those feeding behaviors in male rats which were subject to inhibition by naloxone were characterized by elevated concentration of plasma beta-ep.     

Acute exercise has no effect on ghrelin plasma concentrations.

Exercise is a potent, dose-dependent stimulus of growth hormone (GH) secretion. The hypothalamic peptides, GH-releasing hormone (GHRH) and somatostatin are regarded as major regulators of this stimulation. The role of the stomach-derived peptide ghrelin, which has been shown to exert strong GH releasing effects, has not been fully characterized yet. We therefore studied GH and ghrelin plasma concentrations in response to graded levels of exercise in eight healthy young volunteers. After determination of their individual maximal exercise capacity, all individuals underwent a treadmill exercise at 50 %, 70 %, and 90 % of maximum oxygen consumption (VO (2)max) on different days. Maximal GH response to exercise was observed after 40 minutes at 50 % VO (2)max and after 20 minutes at 70 and 90 % VO (2max). GH serum concentrations increased significantly at all three exercise intensities (GH peak concentrations were 5.8 +/- 2.3 ng/ml, 12.0 +/- 3.2 ng/ml, and 9.8 +/- 4.7 ng/ml, respectively). In contrast, ghrelin plasma concentrations remained unchanged at all three workloads. Assuming that the sensitivity of the GH neuroendocrine/metabolic regulation of GH is unaltered, ghrelin does not participate in the regulation of the GH response to exercise in healthy males.     

Effects of beta-endorphin on body temperature in mice at different ambient temperatures

The effect of intracerebroventricular injection of beta-endorphin (beta-END) on body temperature of mice was studied at ambient temperatures (Ta) of 10 degrees, 20 degrees and 31 degrees C. Doses between 0.1 and 10.0 microgram/mouse were studied. The lower (less than 1 microgram) doses of beta-END produced a hyperthermia at all Ta's studied. The higher doses of beta-END produced hyper- or hypothermia depending on the Ta. The subcutaneous injection of naloxone (1 mg/kg) antagonized the high dose hypothermic effects, but not the hyperthermic effect of beta-END. These data suggest that there may be different receptors and/or sites of action for high and low doses of beta-END.     

Intraerythrocyte and plasma lactate concentrations during exercise in humans

The purpose of this study was to examine plasma and intraerythrocyte lactate concentrations during graded exercise in humans. Seven adult volunteers performed a maximum O2 uptake (VO2max) test on a cycle ergometer. Plasma and intraerythrocyte lactate concentrations (mmol . L-1 of plasma or cell water) were determined at rest, during exercise, and at 15-min post-exercise. The results show that plasma and intraerythrocyte lactate concentrations were not significantly different from each other at rest or moderate (less than or equal to 50% VO2max) exercise. However, the plasma concentrations were significantly increased over the intraerythrocyte levels at 75% and 100% VO2max. The plasma to red cell lactate gradient reached a mean (+/- SE) 1.7 +/- 0.4 mmol . L-1 of H2O at exhaustion, and was linearly (r = 0.84) related to the plasma lactate concentration during exercise. Interestingly, at 15-min post-exercise the direction of the lactate gradient was reversed, with the mean intraerythrocyte concentration now being significantly increased over that found in the plasma. These results suggest that the erythrocyte membrane provides a barrier to the flux of lactate between plasma and red cells during rapidly changing blood lactate levels. Furthermore, these data add to the growing body of research that indicates that lactate is not evenly distributed in the various water compartments of the body during non-steady state exercise.     

Effects of conditioned fear and environmental novelty on plasma beta-endorphin in the rat

The levels of rat plasma beta-endorphin-like immunoreactivity following a 30 min exposure to (1) an unfamiliar operant chamber, (2) an unfamiliar operant chamber providing a VI-5 second schedule of 3 mA, 1 sec footshocks, or (3) a familiar chamber providing no shocks, but previously paired with unavoidable shocks were compared to control values from animals left undisturbed in their familiar home cages. The shocked group showed ten-fold elevations of beta-endorphin-like immunoreactivity compared to the undisturbed control animals, while conditioned rats showed a smaller two-fold elevation when re-exposed to a chamber in which they had previously been shocked. Two of five rats exposed merely to an unfamiliar chamber showed elevations, but there was no statistically reliable group effect. Such procedures may be useful for controlled and parametric studies of the mobilization of pituitary or brain pools of beta-endorphin under conditions involving merely anticipation of pain rather than the actual activation of ascending nervous pain pathways.     

Effects of inflammatory disease on plasma oxprenolol concentrations.

When single oral doses of oxprenolol were given to three healthy subjects on three separate occasions under standardised conditions the plasma concentration-time curves for each subject were closely similar. In two of the subjects, however, a mild illness led to a dramatic, temporary increase in the peak plasma concentration and area under the plasma concentration-time curve (AUC). This effect of inflammatory disease was confirmed by comparing a group of patients with an erythrocyte sedimentation rate (ESR) of over 20 mm in the first hour with a group whose ESR was below this value. The mean peak plasma concentration and AUC were significantly higher in the group with a raised ESR. This may be related to altered concentrations of one of the acute-phase proteins. Thus it is concluded that plasma oxprenolol concentrations are raised in inflammatory disease, but further work is needed to determine the mechanism of this increase.     

Overnight responses of the circulating IGF-I system after acute, heavy-resistance exercise.

This study evaluated the individual components of the insulin-like growth factor I (IGF-I) system [i.e., total and free IGF-I, insulin-like growth factor binding protein (IGFBP)-2 and -3, and the acid-labile subunit (ALS)] in 10 young, healthy men (age: 22 +/- 1 yr, height: 177 +/- 2 cm, weight: 79 +/- 3 kg, body fat: 11 +/- 1%) overnight for 13 h after two conditions: a resting control (Con) and an acute, heavy-resistance exercise protocol (Ex). The Ex was a high-volume, multiset exercise protocol that alternated between 10- and 5-repetition maximum sets with 90-s rest periods between sets. The Ex was performed from 1500 to 1700; blood was obtained immediately postexercise and sampled throughout the night (every 10 min for the first hour and every hour thereafter) until 0600 the next morning. For the first hour, significant differences (P < or = 0.05) were only observed for IGFBP-3 (Ex: 3,801 > Con: 3,531 ng/ml). For the overnight responses, no differences were observed for total or free IGF-I or IGFBP-3, whereas IGFBP-2 increased (Ex: 561 > Con: 500 ng/ml) and ALS decreased (Ex: 35 < Con: 39 microg/ml) after exercise. The results from this study suggest that the impact that resistance exercise exerts on the circulating IGF-I system is not in the alteration of the amount of IGF-I but rather of the manner in which IGF-I is partitioned among its family of binding proteins. Thus acute, heavy-resistance exercise can lead to alterations in the IGF-I system that can be detected in the systemic circulation.     

Elevated plasma and tissue concentrations of beta-endorphin and beta-lipotropin associated with an ectopic ACTH-producing lung tumor

beta-Endorphin- and ACTH-like immunoreactive peptides were measured in plasma and certain tissues of a patient suffering from an oat-cell-carcinoma of the lungs and Cushing's syndrome. Using sensitive radioimmunoassays in combination with gel-filtration, highly elevated levels of beta-endorphin, beta-lipotropin (beta-LPH), alpha-melanotropin (alpha-MSH) and ACTH were found.     

Increase of beta-endorphin concentrations in the plasma and pituitary neuro-intermediate lobe of the rat on the afternoon of proestrus

Beta-endorphin (beta-EP) concentrations in the plasma and the anterior and neuro-intermediate lobes of the pituitary (AP and NIL) were quantitated by radioimmunoassay (RIA) and gel filtration chromatography in female rats at 1000, 1400, and 1900 h on the day of proestrus and diestrus day-1. There were no significant changes in beta-EP in the plasma, AP, or NIL on diestrus day-1. On proestrus, beta-EP in the plasma and NIL, but not the AP, increased significantly from 1000 to 1400 h and returned to basal levels by 1900 h. The time course of this increase of beta-EP in the NIL and plasma is consistent with the temporal sequence of the prolactin and gonadotropin surges on the afternoon of proestrus, suggesting that beta-EP in the NIL may be involved in the regulation of these neuroendocrine events.