Bouts Of Anaerobic Exercise Research Articles

Essential roles of the cytokine oncostatin M in crosstalk between muscle fibers and immune cells in skeletal muscle after aerobic exercise

Crosstalk between muscle fibers and immune cells is well known in the processes of muscle repair after exercise, especially resistance exercise. In aerobic exercise, however, this crosstalk is not fully understood. In the present study, we found that macrophages, especially anti-inflammatory (M2) macrophages, and neutrophils accumulated in skeletal muscles of mice 24h after a single bout of an aerobic exercise. The expression of oncostatin M (OSM), a member of the interleukin 6 family of cytokines, was also increased in muscle fibers immediately after the exercise. In addition, we determined that deficiency of OSM in mice inhibited the exercise-induced accumulation of M2 macrophages and neutrophils, whereas intramuscular injection of OSM increased these immune cells in skeletal muscles. Furthermore, the chemokines related to the recruitment of macrophages and neutrophils were induced in skeletal muscles after aerobic exercise, which were attenuated in OSM-deficient mice. Among them, CC chemokine ligand 2, CC chemokine ligand 7, and CXC chemokine ligand 1 were induced by OSM in skeletal muscles. Next, we analyzed the direct effects of OSM on the skeletal muscle macrophages, because the OSM receptor β subunit was expressed predominantly in macrophages in the skeletal muscle. OSM directly induced the expression of these chemokines and anti-inflammatory markers in the skeletal muscle macrophages. From these findings, we conclude that OSM is essential for aerobic exercise-induced accumulation of M2 macrophages and neutrophils in the skeletal muscle partly through the regulation of chemokine expression in macrophages.

Abstract 10585: Racial Differences in Arterial Stiffness Following Acute Bouts of Anaerobic Exercise

African Americans (AA) experience an exaggerated hemodynamic response during recovery from aerobic exercise compared to Caucasian Americans (CA). There is also evidence that local arterial stiffness increases and systemic vasculature stiffness decreases following aerobic exercise. Despite the growing popularity of high-intensity anaerobic exercise, no study has examined racial differences in arterial stiffness following maximal anaerobic exercise between AA and CA women. Purpose: To compare local and systemic arterial stiffness during recovery from repeated bouts of maximal anaerobic exercise in young, healthy AA and CA women. Methods: Twenty (AA: n=8, age = 22±1yrs, BMI = 24.7±0.8 kg/m 2 ; CA: n=12, age = 22±1 yrs, BMI = 22.9 ±0.7 kg/m 2 ) healthy women without hypertension completed two bouts of maximal anaerobic exercise on a cycle ergometer with 30 minutes of recovery between bouts. Hemodynamic measurements were taken at resting, and 5 (P5-post-EX1), 15 (P15 post-EX1), and 30 minutes (P30 post-EX1) following a maximal anaerobic exercise test on cycle ergometer, and 5 (P5 post-EX2), 15 (P15 post-EX2), and 30 (P30 post-EX2) minutes following the second maximal anaerobic exercise test. Local carotid arterial compliance (AC) was assessed using ultrasonography and systemic arterial stiffness was assessed by augmentation index (AIx@75) and segmental arterial stiffness assessed by central Pulse Wave Velocity (cPWV) using SphygmoCor. Data were analyzed by 2 by 7 (race *time) repeated measures ANOVA. Results: See Table 1. Conclusion: There is less variation in local carotid arterial compliance in AA women compared to CA women following repeated bouts of maximal anaerobic exercise despite similar systemic or segmental arterial stiffness. Racial differences in arterial distensibility between AA and CA women in response to maximal anaerobic exercise may be limited to localized changes in the predominantly elastic carotid artery.

Racial Differences In Cardiovascular Responses Following Acute Bouts Of Anaerobic Exercise

Despite the growing popularity of high-intensity anaerobic exercise, few studies have examined the acute effects of this form of exercise on cardiovascular hemodynamics, or potential racial differences in these responses. In addition, post exercise hypotension may be absent in African Americans (AA) following aerobic exercise, consistent with their higher risk for hypertension. It is unknown whether AA and Caucasian Americans (CA) would exhibit different blood pressures following acute bouts of anaerobic exercise. PURPOSE: To assess hemodynamic changes in healthy, young AA and CA women following repeated bouts (two) of maximal anaerobic exercise. METHODS: Eight young, healthy AA women and 9 CA women completed this study. Vascular and hemodynamic measurements were taken at rest, and 5 (P5-1st), 15 (P15-1st), and 30 minutes (P30-1st) following a maximal anaerobic exercise test on cycle ergometer, and 5 (P5-2nd), 15 (P15-2nd), and 30 (P30-2nd) minutes following the second maximal anaerobic exercise test. Brachial systolic (SBP), diastolic (DBP) blood pressures, central aortic SBP, DBP and mean arterial blood pressure (aortic MAP) were measured. Carotid arterial stiffness (beta-stiffness index) were obtained using ultrasonography. RESULTS: Data were presented in Table 1 as mean ± standard error. Resting DBP and aortic DBP were significantly different between AA and CA (§ p<0.05). There was a significant race by time interaction for aortic MAP (* p<0.05). And there was a trend towards significance in race by time interaction for beta stiffness index (p=0.06). CONCLUSION: Acute bouts of anaerobic exercise increase aortic MAP in young AA but not in CA, and it may be related to increases in arterial stiffness in AA. The heightened BP and vascular responses to exercise stimulus may play a role in the pathogenesis of hypertension in AA. Supported by New England ACSM New Investigator Award to HY.Table 1: Hemodynamic responses to two acute bouts of maximal anaerobic exercise.

The effects of varying doses of caffeine on cardiac parasympathetic reactivation following an acute bout of anaerobic exercise in recreational athletes

BackgroundTo examine the effects of varying doses of caffeine on autonomic reactivation following anaerobic exercise.MethodsRecreationally active males (N = 20; 24 ± 2y) participated in a randomized, double-blind, placebo-controlled, crossover study where participants ingested: [1] Control (CON; no supplement), [2] a non-caffeinated placebo (PLA), [3] 3-mg∙kg− 1 of caffeine (CAF3) or [4] 6-mg∙kg− 1 of caffeine (CAF6) prior to Wingate testing. Parasympathetic (lnRMSSD, primary outcome) and global HRV (lnSDNN, secondary outcome) were assessed at rest (i.e., pre-ingestion), 45-min post-ingestion, and 5-min and 35-min post-exercise recovery. We used a GLM to assess mean (95% CI) changes from pre-ingestion baseline.ResultsOverall, we observed a significant trend for lnRMSSD and lnSDNN (both, p = 0.001, ηp2 = 0.745). Forty-five minutes after treatment ingestion, we observed a significant increase in lnRMSSD for CAF3 (0.15 ms, 95%CI, 0.07,0.24) and CAF6 (0.16 ms, 95%CI, 0.06,0.25), both being significant (both, p < 0.004) vs. CON (− 0.02 ms, 95%CI, − 0.09,0.04). Five-minutes after exercise, all treatments demonstrated significant declines in lnRMSSD vs. baseline (all, p < 0.001). After 35-min of recovery, lnRMSSD returned to a level not significantly different than baseline for CAF3 (0.03 ms, 95%CI, − 0.05, 0.12) and CAF6 (− 0.03 ms, 95%CI, − 0.17, 0.10), while PLA (− 0.16 ms, 95%CI, − 0.25, − 0.06) and CON (− 0.17 ms, 95%CI, − 0.28, − 0.07) treatments remained significantly depressed. A similar pattern was also observed for SDNN.ConclusionCaffeine ingestion increases resting cardiac autonomic modulation and accelerates post-exercise autonomic recovery after a bout of anaerobic exercise in recreationally active young men. However, no differences between caffeine doses on cardiac autonomic reactivity were observed.

The Effects of Stretching on Blood Lactate Concentration after Anaerobic Exercise

Blood lactate (BLa) concentration is believed to be one of the contributing factors of muscular fatigue and muscle soreness when lactate is converted into lactic acid. Because of these decrements associated with BLa accumulation during exercise, multiple methods to remove BLa have been investigated. However, the results on the effects of stretching remain inconclusive. Although BLa returns to resting levels within 30-60 minutes after exercise, the primary focus of this study was to further explore the effects of stretching on BLa recovery. PURPOSE: This study aimed to assess the benefits of stretching on BLa levels (mmol/L) after performing a maximal anaerobic exercise compared to sitting down after the same anaerobic maximal exercise. METHODS: After measuring descriptive data (age, ht., wt., age), 15 subjects (age 22 + 1 years; ht. 1.76 + 0.09 m; wt. 83 + 15 kg) performed a Wingate Cycle Ergometer Test, on two separate occasions, followed by two different 10-minute protocols in counterbalanced order: sitting or (active and passive) stretching. BLa levels were measured before and after performing the Wingate test and then 10 minutes after the test. RESULTS: The difference in BLa levels before (p = 0.815) and after (p = 0.212) exercise were similar and showed no significant difference (p < 0.05). However, there was a statistically significant difference in BLa levels between the two post 10-minutes protocols (p = 0.002). CONCLUSIONS: The current results indicate that stretching after a maximal bout of anaerobic exercise can be statistically significant in lowering BLa accumulation.

Effect of listening to music during a warmup on anaerobic test performance

Many studies have investigated the effect of listening to music during exercise on performance, but the influence of music during a warmup on subsequent exercise performance is unknown. The primary purpose of this study was to determine whether or not listening to self-selected music before an intense bout of anaerobic exercise would positively affect performance. We also sought to explore the effect of music on psychological variables including rating of perceived exertion (RPE). 16 participants (8 males, 8 females; age 23.6 ± 4.8 years, BMI 18.9 ± 3.2 kg/m2) listened to pre-selected music, self-selected music or white noise during a warmup, which consisted of cycling at 50 rpm for 10 min with a resistance of 1 kg. Once the warmup was completed, they performed a Wingate Anaerobic Test (WAnT) against a flywheel resistance of 7.5% body mass. Immediately after the WAnT, they were asked to complete the Subjective Exercise Experience Scale (SEES) and RPE was assessed. One-way repeated-measures ANOVAs were used to determine the effect of music condition on both physiological and psychological variables. There were no significant differences in mean or peak power, relative power, fatigue index, or RPE (all p > 0.05). There were also no differences in any SEES variables (positive well-being, psychological distress, or fatigue) or in RPE (all p > 0.05). This study suggests that listening to music during a warmup has no positive effect on performance during the actual event, even when the music is self-selected.

Effect of nicotine on repeated bouts of anaerobic exercise in nicotine naïve individuals.

Nicotine is a psychostimulant that is reported to be commonly supplemented by athletes. The purpose of the current study was to determine the effects of a rapidly absorbed form of nicotine on repeated bouts of anaerobic exercise, perception of exertion and a range of cardiovascular variables while monitoring side effect profiles. Sixteen healthy, nicotine naïve male athletes (24.1 ± 5.3years, 179.0 ± 8.8cm, 81.7 ± 13.5kg, BMI 25.5 ± 3.0, Body fat% 13.2 ± 5.1%) completed two repeated 30s Wingate tests with 3min rest between bouts following consumption of either a 5-mg oral-dispersible nicotine strip (NIC) or a flavour-matched placebo (PLA) in a randomised, double-blind, cross-over design. Before the Wingate test, resting heart rate and blood pressure were also measured prior to and following PLA and NIC ingestion. Peak and average power output were significantly greater following NIC administration compared to PLA (P < 0.01). Similarly, significant increases were also seen in heart rate and blood pressure following NIC administration compared to PLA (P < 0.01). No significant effect on pre-exercise side effect score, reaction time, rate of perceived exertion or post exercise blood lactate levels were observed (P > 0.05). It was concluded that oral-dispersible nicotine strips increase repeated anaerobic performance, possibly through strong sympathetic stimulation, as evident by significant elevation of cardiovascular parameters.

Pre-exercise alkalosis attenuates the heat shock protein 72 response to a single-bout of anaerobic exercise

The heat shock protein 72 (HSP72) response following exercise is well documented, however, little is known on whether the expression may be mediated by the ingestion of ergogenic aids prior to performance. The purpose of this research was to investigate the effect of sodium bicarbonate (NaHCO 3) ingestion on monocyte and lymphocyte expressed HSP72 and oxidative stress for 4-h post exercise. Seven active males (22.3 ± 2.9 years, 181.6 ± 4.5 cm, 78.1 ± 8.1 kg) performed a 4-min ‘all-out’ cycle test following a dose of 0.3 g kg −1 body mass of NaHCO 3, or an equimolar placebo dose of sodium chloride. HSP72 was measured by flow cytometry and oxidative stress was determined via plasma thiobarbituric acid substances (TBARS) analysis. The NaHCO 3 ingestion significantly increased blood pH ( p < 0.001), bicarbonate ( p < 0.001) and base excess ( p < 0.001) pre-exercise. Despite this there was no evidence of a significantly improved exercise performance when compared with the placebo trials ( p ≥ 0.26) (means ± SD; average power 292 ± 43 W vs. 291 ± 50 W; peak power 770 ± 218 W vs. 775 ± 211 W; work completed 71 ± 10 kJ vs. 68 ± 10 kJ). Monocyte expressed HSP72 was significantly lower under experimental conditions during the 4-h post-exercise ( p = 0.013), as was plasma TBARS ( p < 0.001). These findings suggest that pre-exercise alkalosis can attenuate the stress response to a single bout of anaerobic exercise.

Excess Postexercise Oxygen Consumption following Repeated Bouts of Anaerobic Exercise

PURPOSE: Repeated anaerobic bouts are often used in training and observed in athletic competition. To our knowledge, the elevation in postexercise metabolism following exercise bouts of this nature has not been observed. The purpose of this study was to investigate excess postexercise oxygen consumption (EPOC) following repeated, exhaustive bouts of anaerobic exercise. METHODS: Four recreationally trained male subjects (age: 24.5 + 2.7 yrs), performed nine bouts of anaerobic exercise using the Wingate 30-second cycle protocol. The bouts were separated into sets of three, with a two minute rest after the first and second bout and a six minute forty-five second rest after the third bout, resulting in total test duration of thirty minutes. Prior to the third bout of the third set, subjects were fitted with an appropriate gas collection mask, and calculation of EPOC began immediately following that bout. Subjects reported to the laboratory rested and following a 12-hour fast. Each test was preceded by a 30-minute baseline test to determine resting metabolic rate. Postexercise VO2 was continuously monitored until baseline was re-established. RESULTS: EPOC magnitude and duration from repeated, exhaustive anaerobic exercise bouts was 10.6 + 4.3 L O2 and 58.5 + 38.8 mins, respectively. Heart rate at the completion of recovery was significantly elevated above rest (66.3 + 8.1 bts*min-1 vs. 84.8 + 13.7 bts*min-1, p=.01). CONCLUSIONS: These data indicate that EPOC, and thus caloric expenditure, during recovery from repeated, exhaustive anaerobic bouts of exercise is a noteworthy contributor to total caloric burn following this type of exercise, and is substantially greater than previously published EPOC values reported from aerobic exercise protocols. Heart rate remained significantly elevated above resting levels even after postexercise oxygen consumption returned to baseline. Further investigation of postexercise biomarkers, such as catecholamines, is warranted.

Exercise activation of muscle peroxisome proliferator-activated receptor-γ coactivator-1α signaling is redox sensitive

The peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α)-activated signal transduction pathway has previously been shown to stimulate mitochondrial biogenesis in skeletal muscle in response to endurance exercise. In vitro data indicate that PGC-1α signaling may be sensitive to reactive oxygen species (ROS) but its role in vivo is not clear. The objectives of this study were (1) to investigate whether the PGC-1α pathway could be activated by a single bout of anaerobic exercise in rats, wherein a major portion of ROS was generated via the cytosolic xanthine oxidase (XO), and (2) to examine whether allopurinol (ALP), a specific XO inhibitor, would attenuate PGC-1α expression and signaling owing to decreased ROS generation. Female Sprague–Dawley rats were randomly divided into three groups: (1) subjected to sprinting on a treadmill at 35 m/min, 15% grade, for 3 min followed by 3 min slow running at 15 m/min, 0% grade, repeated until exhaustion (88 ± 4 min; Exer; N = 9); (2) subjected to the same exercise protocol (88 ± 4 min) but injected with two doses of ALP (0.4 mmol/kg, ip) 24 and 1 h before the experiment (Exer+ ALP; N = 9); and (3) rested control (C; N = 9). Exercise increased XO activity and ROS generation in the Exer rat vastus lateralis muscle ( P < 0.05), whereas the Exer+ ALP group displayed only 7% XO activity and similar ROS level compared with the C group. PGC-1α protein content showed a 5.6-fold increase ( P < 0.01) in Exer vs C, along with a 200% ( P < 0.01) increase in both nuclear respiratory factor (NRF)-1 and mitochondrial transcription factor A (Tfam) content. ALP treatment decreased PGC-1α, NRF-1, and Tfam levels by 45, 19, and 20% ( P < 0.05), respectively. Exercise doubled the content of the phosphorylated cAMP-responsive element-binding protein in the Exer group ( P < 0.01) and tripled phosphorylated p38 mitogen-activated protein kinase ( P < 0.01), whereas these effects were reduced by 60 and 30% ( P < 0.01, P < 0.05), respectively, in Exer+ ALP rats. Nuclear factor-κB binding and phospho-IκB content were also increased in Exer rats ( P < 0.01) and these increases were abolished by ALP treatment. The data indicate that contraction-activated PGC-1α signaling pathways in skeletal muscle are redox sensitive and that nonmitochondrial ROS play an important role in stimulating mitochondrial biogenesis.

Dose-related Effects of Sodium Bicarbonate Ingestion on Acid-base Balance During Exhausting Anaerobic Exercise

1166 Anaerobic exercise causes significant acid-base balance perturbations. It has been suggested that sodium bicarbonate (NaHCO3) may prevent a significant pH drop during anaerobic exercise resulting in performance enhancement. PURPOSE: To determine whether two intake levels of short-term NaHCO3 supplementation alters acid-base balance and performance during an acute bout of anaerobic exercise. METHODS: Twenty-four men (22 ± 1.77 yrs, 77.5 ± 7.8 kg, 1.79 ± 6.6 m, and a VO2max of 51.03 ± 7.53 ml/kg/min) participated in the present study. Subjects were randomly assigned to one of 3 groups (n = 8/group): control (C, sugar-free mixed fruit placebo), moderate NaHCO3 intake (MI, 0.3 gr/kg), and high NaHCO3 intake (HI, 0.5 gr/kg). Participants consumed either placebo or NaHCO3 for 6 days. pH, HCO3, PO2, PCO2, and lactate in arterialised blood as well as mean cycling power were determined prior to and immediately following a Wingate test (before and following the supplementation period). Data were analysed by ANOVA repeated measures. RESULTS: There was a significant increase (p<0.001) in post blood bicarbonate in MI and HI, and the elevation was incrementally related to the dosage. Exercise in C caused a reduction (p<0.05) of pH (7.42 ± 0.01 at rest vs. 7.15 ± 0.02 post-exercise) and PCO2 (mmHg) (39.8 ± 2.3 at rest vs. 34.3 ± 1.9 post-exercise) and an increase (p<0.001) of lactate (mM) (0.9 ± 0.1 at rest vs. 10.9 ± 2.0 post-exercise). Mean power (W/kg) increased (p<0.05) after supplementation in MI (7.36 ± 1.33 vs. 6.73 ± 0.95) and HI (7.72 ± 1.24 vs. 6.69 ± 1.38) with HI being more effective (p<0.05) than MI. After NaHCO3 ingestion, blood lactate (mM) was higher (p<0.05) during exercise in MI (12.3 ± 1.5 vs. 10.3 ± 2.1) and HI (12.4 ± 1.8 vs. 10.2 ± 1.1). pH was significantly (p<0.05) elevated post-exercise when NaHCO3 was ingested (7.305 ± 0.03 vs. 7.198 ± 0.02 in MI and 7.343 ± 0.02 vs. 7.2 ± 0.01 in HI). HCO3 decreased (p<0.05) with NaHCO3 ingestion post-exercise (29.8 ± 3.3 vs. 17.56 ± 2.5 in MI and 19.8 ± 3.2 vs. 32.3 ± 4.1 in HI). PO2 (mmHg) increased (p<0.05) with NaHCO3 consumption post-exercise (113.3 ± 7.7 vs. 93.2 ± 6.9 in MI and 116.7 ± 8.2 vs. 92.7 ± 7.5 in HI) with HI being more effective (P<0.05) than MI. PCO2 declined (p<0.05) with NaHCO3 supplementation post-exercise (42.8 ± 3.3 vs. 36.2 ± 2.9 in MI and 44.2 ± 5.3 vs. 34.8 ± 4.1 in HI) with HI being more effective (P<0.05) than MI. CONCLUSIONS: Short-term NaHCO3 ingestion may be beneficial for protecting against acid-base balance disturbances and improve performance during acute anaerobic exercise. However, it appears that this NaHCO3-effect on acid-base balance and performance is dose-related with higher intakes being more effective.

THE EFFECTS OF ACUTE BOUTS OF AEROBIC AND ANAEROBIC EXERCISE ON MOOD STATES

In previous psychophysiological research, the relationship between physical activity and various psychological indices following weeks of training has been examined. The purpose of this study was to determine the effect of two bouts of maximal aerobic exercise (Bruce and Ramp protocols) and one bout of anaerobic exercise on the mood states of college-aged males. Ten subjects were oriented to the treadmill and mouthpiece and baseline data gathered on the first visit. The additional 3 visits were randomly ordered for the Bruce, Ramp and Wingate tests. Prior to exercising and again when finished the Activation-Deactivation Adjective Check List (AC-ADL) was administered. The AC-ADL is a measure of high and low affective states and is regarded as a viable tool for assessing mood states in exercise settings. Statistical analysis of the physiological variables (VO2max, HRmax, and VEmax) indicated no significant differences between the Bruce and Ramp protocols. Multiple pairwise comparisons of the four AD-ACL categories for all three of the exercise tests reflected no significant differences between the pre and post-test scores or post-test scores across modality.

CREATINE SUPPLEMENTATION AND ACUTE DEHYDRATION

1276 Creatine (Cr), a widely used dietary supplement, has been demonstrated to enhance muscular strength and anaerobic power. However, coaches, trainers, professional sports teams, and physicians have raised concerns regarding its safety. There is specific concern with numerous anecdotal reports suggesting that Cr supplementation will compromise an individual's heat tolerance during exercise, subsequently leading to an increase of skeletal muscle cramping and tearing. The purpose of this study was to investigate the effects of oral Cr supplementation and acute dehydration on plasma volume, electrolyte and mineral balance, and anaerobic exercise performance. Using a randomized double-blind design, 15 subjects ingested either 20 g·d1 of Cr monohydrate (CR) (N=8) or a placebo (PL) (N=7) for 5-d and then undertook two consecutive 80-min dehydration protocols resulting in −1.5% (D1) and −3% (D2) decreases in body mass (BM). After 5-d of supplementation, there was a significant increase in BM in both groups (PL: 0.6 ±0.5; CR:1.5 ±0.1 kg), but there was no difference between groups (P = 0.09). There were no significant changes in body composition; plasma volume (PV); serum electrolytes (Na, K, CI), minerals (Mg, Zn, Ca), osmolality; and anaerobic exercise performance measures of maximum power (MP), total work (TW), or fatigue index (FI) as determined from ten, 6-s sprints on a cycle ergometer. As expected, the two 80-min dehydration sessions resulted in a significant ΔPV in both groups at D1 (PL: −10.9±2.0; CR: −9.2±1.6%) and D2 (PL: −15.6±2.1; CR: −16.5±1.6%) but, no difference between groups. There were no significant differences between groups at either D1 or D2 for measures of serum electrolytes, minerals, osmolality, MP, TW, or FI. The results suggest that a 5-d loading dose of Cr does not negatively affect plasma volume or serum electrolyte and mineral balance. However, it also does not appear to enhance the performance of repeated bouts of anaerobic exercise. Supplement provided by Experimental and Applied Sciences, Inc.

EFFECTS OF PRIOR WEIGHT TRAINING EXERCISE ON FUEL UTILIZATION DURING AEROBIC RUNNING.

1138 The purpose of this study was to determine the effect of preceding an aerobic running bout by weight training on fuel utilization. Moderately trained subjects (9 M, 7 F) preceded a 20-min aerobic treadmill run at 60-70% VO2max by either no exercise (NE) or a 6-exercise weight training circuit (CT). Each exercise was performed for 10-12 repetitions to muscular fatigue on big-muscle exercises, with a 3-min recovery between exercises. Metabolic responses during the run were measured by an automated cart, and HR was measured by a Polar watch. Dependent t-tests indicated that RER was significantly lower and HR was significantly higher during the CT trial than during the NE trial, with VO2 and caloric expenditure remaining nonsignificantly different. These findings indicated a shift toward greater fat utilization during aerobic exercise when it is preceded by a bout of anaerobic exercise like weight training. TableTable

The metabolic potential of hepatocytes and kidney tissue in the little skate, Raja erinacea

AbstractIsolated hepatocytes from the little skate (Raja erinacea) are characterized by a general low metabolic activity, which can be explained by the benthic lifestyle of the animal. Of the substrates tested, alanine, serine, and leucine are equally good oxidative substrates, and the highest rates of gluconeogenesis are achieved with alanine and glycerol as carbon sources. In both respects, lactate is a relatively poor substrate, and this probably reflects the low abundance of this potential energy source in the skate, even after bouts of anaerobic exercise. The long chain fatty acid oleate and glycerol are poor oxidative substrates for the hepatocytes, Experiments with 3‐mercaptopicolinate, an inhibitor for phosphoenolypyruvate carboxykinase (PEP CK), reveal that serine is funneled into gluconeogenesis through the serinetransaminase pathway, and PEP CK is bypassed. In vitro, the skate liver cells display the potential to synthesis and export ketone bodies from precursors sush as leucine or oleate, whereas added β‐hydroxybutyrate is poorly oxidized. The skate liver appears to be geared towards export of ketone podies while at the same time conserving glycerol carbon for lipid synthesis. Supplied with precursors such as bicarbonate, blutamine, and aspartate, the cells synthesize urea at a rate 0.85 μmol/g/hr at 10°C. β‐Hydroxybutyrate can acelerate the rate of urea synthesis, probably by increasing the intramitochondrial availability of ATP. Unlike any other vertebrate kidney, the tissue of the little skate appears to play no role in glucose synthesis. Skate kidney is characterized by an active oxidative metabolism and a broad substrate preference, with lactate, serine, alanine, and β‐hydroxybutyrate serving as equally good oxidative fuels.