Biomedical subjects

G Brisson

Publications and source records attributed to G Brisson.

At least 19 recordsLinked to original sources

PubMed1993

Oxidation of ethanol at rest and during prolonged exercise in men.

The purpose of this study was to measure the oxidation of ethanol at rest and during prolonged moderate exercise with use of 13C labeling. Five healthy young males (22.4 +/- 2.7 yr; maximal O2 uptake = 56 +/- 6.6 ml.kg-1.min-1) performed three exercises (68.4 +/- 6.7% maximal O2 uptake; 90 min) on a cycle ergometer with ingestion of 0.4 (trial A) and 0.8 (trial B) g/kg body wt of [13C]ethanol (diluted in 770 +/- 72 ml of water) or water only (trial C). The subjects were also studied during a 90-min rest period after the ingestion of 0.8 g/kg body wt of [13C]ethanol (trial D). At rest, over the 90-min observation period, only 2.1 +/- 0.3 g of the 61.6 +/- 5.7 g of ethanol ingested were oxidized, providing 11.1 +/- 1.9% of the total energy expenditure. Over the 90 min of exercise, the amounts of ethanol oxidized were similar in trials A (9.5 +/- 2.0 g) and B (8.5 +/- 2.5 g). The contribution of ethanol represented 5.2 +/- 1.0% of the total energy expenditure, which is much lower than that previously reported for exogenous carbohydrates (8-18%) or medium-chain free fatty acids (7-14%). The small contribution of ethanol to energy metabolism did not significantly modify endogenous substrate oxidation.

Adult↗

PubMed1993

Comparison of two methods for computing exogenous substrate oxidation using 13C-labeling.

With 13C stable isotope as tracer, the purposes of this study were to measure the oxidation rates of exogenous glucose by using two computation procedures that take into account changes in isotopic composition of CO2 arising from oxidation of endogenous substrates (Rendo) and compare these results with studies using 14C-glucose. Two different low levels of 13C-enrichment were used in the first procedure, while a very high level of enrichment was used in the second one. Each of the eight subjects completed four exercises (68 +/- 5% VO2max; 90 min) on cycle ergometer, at 7-d intervals. After 30 min of exercise, the subjects ingested in a single bolus of 30 g of 13C-glucose, dissolved in 300 ml of water, enriched at three different levels (trials A and B = -10.9 and +2.5; trial C = +291.9/1000 delta 13C-PDB-1), or water only. The metabolic and endocrine state at rest and its response to exercise with or without glucose ingestion were similar in the four trials, with the exception of FFA and glycerol, which were blunted by the ingestion of glucose. As expected, Rendo significantly increased from rest (-22.7 +/- 0.7/1000 delta 13C-PDB-1) to the beginning of exercise without glucose ingestion (-21.2 +/- 0.5/1000 delta 13C-PDB-1). The amounts of exogenous glucose oxidized over the last hour of exercise and computed from trials A and B and from trial C were 14.9 +/- 4.4 and 13.0 +/- 4.2 g, representing 7.4 and 6.3% of the total energy requirement, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Serum gastrin and blood glucose levels during halothane-nitrous oxide anaesthesia and strabismus surgery in children.

The purpose of this study was to determine whether serum gastrin levels are increased by reflexogenic stimuli applied to the extrinsic muscles of the eye. Serum gastrin and blood glucose concentrations were measured in ten normal children aged between 5 and 12 yr during general anaesthesia with halothane and nitrous oxide and during strabismus surgery. Fasting basal concentrations of gastrin (33.6 +/- 14.8 pg.ml-1) and of glucose (4.43 +/- 0.72 mmol.L-1) were in the normal range of values for children. Intravenous atropine (0.01 mg.kg-1), general anaesthesia with halothane in nitrous oxide and oxygen by mask for three minutes, tracheal intubation, extraocular muscle stimulation and surgical stress did not cause any variation in the mean serum gastrin concentration. On the contrary, tracheal intubation and surgical stress increased blood glucose concentrations (P less than 0.05). There was no difference in the serum gastrin levels after extraocular muscle stimulation between children with positive or negative oculocardiac reflexes (44.5 +/- 16.7 pg.ml-1 vs 38 +/- 14.7 pg.ml-1, respectively). The incidence of vomiting predischarge was 60 per cent. Serum gastrin levels did not differ between children who vomited and children who did not (44.3 +/- 18.5 pg.ml-1 vs 47.1 +/- 16.9 pg.ml-1, respectively). Vomiting after strabismus surgery cannot be attributed to high gastrin serum levels. Consequently, it is unlikely that vomiting after strabismus surgery is linked to an "oculogastric reflex" with the vagus nerve as the efferent pathway.

Anesthesia, Inhalation↗

PubMed1991

Plasma atriopeptin response to prolonged cycling in humans.

The exercise-induced increase in plasma atriopeptin (ANP) has been related to exercise intensity. The independent effect of duration on the ANP response to dynamic exercise remains incompletely documented. The purpose of this study was to describe the time course of plasma ANP concentration during a 90-min cycling exercise protocol and to examine this in light of concurrent variations in plasma arginine vasopressin (AVP), aldosterone (ALD), and catecholamine (norepinephrine and epinephrine) concentrations as well as plasma renin activity (PRA). Seven male and four female healthy college students (23 +/- 2 yr) completed a prolonged exercise protocol on a cycle ergometer at an intensity of 67% of maximal O2 uptake. Venous blood was sampled through an indwelling catheter at rest, after 15, 30, 45, 60, and 90 min of exercise, and after 30 min of passive upright recovery. Results (means +/- SE) indicate an increase in ANP from rest (22 +/- 2.6 pg/ml) at 15 min of exercise (45.3 +/- 7.4 pg/ml) with a further increase at 30 min (59.4 +/- 9.8 pg/ml) and a leveling-off thereafter until completion of the exercise protocol (51.7 +/- 10.7 pg/ml). In plasma ALD and PRA, a significant increase was found from rest (ALD, 21.4 +/- 6.4 ng/dl), PRA, 2.5 +/- 0.5 ng.ml-1.h-1 after 30 min of cycling, which continued to increase until completion of the exercise (ALD 46.6 +/- 8.7 ng/dl, PRA 9.5 +/- 0.9 ng.ml-1.h-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Role of the source of phosphate salt in improving the mineral balance of parenterally fed low birth weight infants.

Because the monobasic potassium phosphate salt (monobasic) improves the solubility of calcium and phosphorus in amino acid plus dextrose solutions, compared with the current mixtures of monobasic plus dibasic salts (dibasic), we tested the bioavailability and clinical effects of monobasic in 16 parenterally fed low birth weight infants at standard (n = 8) and high levels (n = 8) of mineral intakes. A constant infusion of macronutrients and vitamin D was provided in a crossover design of two four-day periods. With standard intakes of calcium (35 mg/kg/day, 0.9 mmol/kg/day) and phosphorus (30 mg/kg/day, 1 mmol/kg/day), there was no difference between monobasic and dibasic regimens on balance data or plasma biochemical monitoring (calcium, phosphorus, pH, carbon dioxide pressure, base excess, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D). With the use of the monobasic regimen, the mineral intakes were doubled without precipitation in the infusate: calcium, 70 mg/kg/day (1.8 mmol/kg/day), and phosphorus, 55 mg/kg/day (1.7 mmol/kg/day). This led to increased apparent retention of both calcium (63 +/- 5 mg/kg/day, 1.58 +/- 0.12 mmol/kg/day) and phosphorus (52 +/- 4 mg/kg/day, 1.67 +/- 0.14 mmol/kg/day) compared with that for standard levels of mineral intake. The improvement of calcium-phosphorus balance was accompanied by more severe calciuria (9 +/- 2 mg/kg/day, 0.2 +/- 0.05 mmol/kg/day) and by metabolic compensation for an increased acid load. In addition to the possibility of exceeding the buffering capacity of the infant, this relative acidosis could also be evidence of improved bone mineralization.

Amino Acids↗

PubMed1990

Oxidation of exogenous carbohydrate during prolonged exercise in fed and fasted conditions.

The oxidation of glucose and fructose ingested during moderate exercise performed on a cycle ergometer (120 min, 52% VO2max) was compared in ten young males fasted (n = 5) or fed (n = 5) before exercise. The subjects ingested randomly 1.33 g/kg body weight (approximately 96 +/- 9 g) of either enriched 13C-glucose (G), 13C-fructose (F), or water only (W); the solutions were evenly distributed over the exercise period. The fasted subjects began the three exercises with a lower blood glucose (P less than or equal to 0.05 for F only) and insulin (P less than or equal to 0.05) levels and a higher free fatty acid (FFA) concentration (P less than or equal to 0.05) than the fed ones. Throughout the exercise period, blood glucose level was maintained in fasted as well as in fed group for G and F ingestions, while it decreased (P less than or equal to 0.05 at the 100th min in fasted subjects) with water ingestion. Insulin level was similar in both fed and fasted conditions with F and W ingestions and lower than G trials for the fed subjects. For the three ingestions, FFA was lower (P less than or equal to 0.05) in the fasted than in the fed group over the exercise period. Over the 2-h period of exercise, a greater (P less than or equal to 0.05) amount of exogenous F was oxidized in the fasted (49 +/- 6 g) than in the fed (36 +/- 5 g) group, which represent 31% and 20% of the total carbohydrate energy supply, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary Carbohydrates↗

PubMed1990

Plasma catecholamines in the aorta and the phrenicoabdominal vein in exercising dogs.

Plasma epinephrine and norepinephrine concentrations were measured in the aorta and phrenicoabdominal vein in five dogs at rest and during short-duration mild- and moderate-intensity exercise and during prolonged mild-intensity exercise. Plasma epinephrine and norepinephrine concentrations increased with exercise in both the aorta and the phrenicoabdominal vein. Plasma epinephrine concentration was much higher in the phrenicoabdominal vein than in the aorta (24-43 times). Plasma epinephrine concentrations in the aorta and phrenicoabdominal vein were significantly correlated (r = 0.88). This confirms that peripheral epinephrine concentration is a reliable index of the activity of the adrenal medulla during exercise. The epinephrine-to-norepinephrine ratio in the phrenicoabdominal vein was stable (4:1) throughout the experimental protocol, suggesting that the proportion of the two amines released by the adrenal medulla did not vary through this range of adrenal activity in dogs.

Adrenal Medulla↗

PubMed1990

Use of 13C substrates for metabolic studies in exercise: methodological considerations.

The purpose of this study is to outline a common mistake made when the rate of oxidation of exogenous substrates during prolonged exercise is computed using 13C naturally labeled substrates. The equation proposed and commonly used in the computation does not take into account that exercise and/or exogenous substrate ingestion modifies the composition of the mixture of endogenous substrates oxidized and, consequently, the isotopic composition of CO2 arising from oxidation of endogenous substrates. The recovery of 13C and the amount of exogenous substrate oxidized are thus overestimated. An adequate procedure for the computation of exogenous substrate oxidation taking into account changes in isotopic composition of CO2 arising from oxidation of endogenous substrates is suggested. Results from a pilot experiment (4 subjects) using this procedure indicate that over 2 h of exercise (66% of maximal O2 uptake), with ingestion of 60 g of glucose, 39 +/- 4 g of glucose were oxidized. Estimates made without taking into account changes in isotopic composition of CO2 arising from oxidation of endogenous substrates range between 70 +/- 8 and 44 +/- 3 g depending on 1) the isotopic composition of exogenous glucose and 2) the isotopic composition of expired CO2 taken as reference (rest or exercise without glucose ingestion). These observations suggest that results from previous studies of exogenous substrate oxidation during exercise using 13C labeling should be used with caution.

Acetyl Coenzyme A↗

PubMed1990

6-OHDA sympathectomy and exercise performance in the rat.

6-hydroxydopamine (6-OHDA) was utilised for the study of the sympathetic nervous system in the resting rats and rats submitted to prolonged exercise. In order to reduce the acute physiological stress associated with an injection of 6-OHDA, beta-1 and alpha-1 adrenoceptors were blocked before the treatment leading to sympathectomy. Sympathectomised rats were divided in two groups: one sacrificed at rest, 24 hours after the treatment. The other group was sacrificed after a treadmill exercise to exhaustion. Running time to exhaustion was 36.0 +/- 4.5 min (mean +/- S.E.M.). This group ran significantly less than a control group brought to exhaustion in 73.7 +/- 10.0 min of exercise (P < 0.05). In order to make appropriate comparisons, another control group was run for 36 min. Some differences were observed between corresponding control and sympathectomized groups. At rest: 1) a lower plasma level of insulin, and 2) a higher plasma free fatty acid concentration were observed in sympathectomized rats. After 36 min of exercise: 1) a lower plasma concentration of norepinephrine, 2) no decrease of the plasma level of insulin, 3) no increase in the plasma glucagon concentration, and 4) a higher plasma glucose level were observed in sympathectomised rats when compared to control rats running for the same time. The lower plasma norepinephrine concentration in exercised sympathectomised rats suggests a lower sympathetic nervous activity in these animals than in control rats. The absence of a decrease of plasma insulin concentration and of an increase in glucagon can be attributed to this lower sympathetic activity in sympathectomised rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Blood pressure and plasma catecholamine responses to various challenges during exercise-recovery in man.

The purpose of this study was to assess the effects of a 2 h cycle exercise (50% VO2max) on heart rate (HR) and blood pressure (BP), and on plasma epinephrine (E) and norepinephrine (NE) concentrations, during the recovery period in seven normotensive subjects. Measurements were made at rest in supine (20 min) and standing (10 min) positions, during isometric exercise (hand-grip, 3 min, 25% maximal voluntary, contraction), in response to a mild psychosocial challenge (Stroop conflicting color word task) and during a 5-min period of light exercise (42 +/- 3% VO2max). Data were compared to measurements taken on another occasion under similar experimental conditions, without a previous exercise bout (control). The results showed HR to be slightly elevated in all conditions following the exercise bout. However, diastolic and systolic BP during the recovery period following exercise were not significantly different from the values observed in the control situation. Plasma NE concentrations in supine position and in response to the various physiological and/or psychosocial challenges were similar in the control situation and during the recovery period following exercise. On the other hand plasma E (nmol.1-1) was about 50% lower at rest (0.11 +/- 0.03 vs 0.23 +/- 0.04) as well as in response to hand-grip (0.21 +/- 0.04 vs 0.41 +/- 0.20) and the Stroop-test (0.21 +/- 0.05 vs 0.41 +/- 0.15) following the exercise bout.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Metabolic and clinical consequences of changing from high-glucose to high-fat regimens in parenterally fed newborn infants.

To evaluate the metabolic and clinical consequences of changing from high-glucose to high-fat regimens during initiation of parenteral nutrition, we performed 22 studies in 11 newborn infants (birth weight (mean +/- SD) 2.54 +/- 0.54 kg, gestational age 37 +/- 3 weeks, postnatal age 8 +/- 3 days) maintained in a constant thermal environment. In a paired design, two isoproteinic (2.4 +/- 0.2 gm/kg/day) and isocaloric (64 +/- 6 kcal/kg/day) regimens differing by source of energy (high glucose vs high lipid) were infused on consecutive days. Environmental and body temperatures were recorded during a 4-hour period, and 24-hour urinary excretions of catecholamines, nitrogen, and C peptide were measured. Despite constant incubator and average skin temperatures, the rectal and interscapular temperatures rose significantly when the high-glucose regimen was changed to a high-lipid regimen. The specific locations of these changes in body temperature suggested brown fat activation. A significant drop in nitrogen retention (63 +/- 9% vs 56 +/- 10%) during the lipid infusion could be further evidence of a metabolic adaptation to the rapid change in energy substrates.

C-Peptide↗

PubMed1989

Iron deficiency among active men.

Iron deficiency in active men is well documented. To assess the relative importance of dietary iron intake, iron absorption, and iron loss in the pathogenesis of this iron deficiency, we compared a group of iron-deficient athletes to a group with normal iron stores. Iron absorption was assessed by an iron tolerance test. Serum haptoglobin was used as a measure of hemolysis. The presence of hemoglobinuria reflected urinary iron loss. Iron intake was determined by a 3-day dietary record as well as a food frequency questionnaire. Results showed iron absorption to be inversely correlated with iron stores. Iron-deficient athletes had higher absorption, suggesting a normal regulation mechanism. Major hemolysis (serum haptoglobin below 40 mg/dl) was found in 28% of subjects with no relationship to iron stores. No hemoglobinuria was detected after a usual training session. Iron intake was elevated in relation to high caloric intake, but iron intake in the form of meat was lower in iron-deficient athletes, as compared to those with normal or repleted iron stores. It is our opinion that inadequate iron intake is an important determinant of iron deficiency in athletes.

Absorption↗

PubMed1989

Metabolic and endocrine responses to prolonged exercise in rats under beta 2-adrenergic blockade.

The respective roles of allosteric regulators and catecholamines in the control of muscle glycogen breakdown during exercise remain a matter of controversy. This study was designed to reassess the role of the sympathoadrenal system during prolonged exercise in rats. Animals were studied at rest or after treadmill exercise (28 m.min-1; 8% slope) to exhaustion in a control situation or following administration of a specific beta 2-adrenergic receptor antagonist (ICI 118,551, 1 mg.kg-1, i.v.). Running times to exhaustion were 54 and 36 min in control and treated rats, respectively. For the purpose of comparison, another group of control rats was studied after a 36-min exercise bout. The reduction in endurance in treated rats was associated with an impairment in glycogen utilization, as measured by muscle glycogen stores, in soleus muscle but not in superficial vastus lateralis or gastrocnemius lateralis muscles. Utilization of liver glycogen stores was similar in the two groups of animals, but plasma glucose (7 vs. 13 mM) and lactate (4 vs. 7 mM) levels were significantly lower in rats under beta-blockade than in control rats run for 36 min. Plasma free fatty acid and glycerol concentrations were not significantly different between groups. On the other hand, plasma epinephrine concentration was significantly higher in treated rats (13 vs. 5 mM), which might reflect a compensatory increase in adrenal activity. These results suggest that glycogen breakdown during prolonged exercise is under the control of the sympathoadrenal system in predominantly slow-twitch but not in predominantly fast-twitch muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗

PubMed1989

Plasma atriopeptin during exercise in dogs under beta-blockade.

The purpose of this study was to describe plasma atriopeptin concentrations at rest and in response to moderate treadmill exercise (10 min, 4 km/h, 26% slope) performed with or without nonspecific beta-adrenergic blockade (1 mg/kg iv propranolol) in 10 mongrel dogs [19 +/- 2 (SE) kg]. A small (20%) but significant (P less than 0.05) increase in plasma atriopeptin concentration was observed from rest (43 +/- 5 pg/ml) to exercise (52 +/- 6 pg/ml) without beta-blockade. Propranolol significantly reduced heart rate at rest (89 +/- 7 vs. 104 +/- 7 beats/min) and during exercise (96 +/- 10 vs. 176 +/- 11 beats/min), and this was associated with a larger increase in plasma atriopeptin concentration during exercise (rest 46 +/- 6 pg/ml; exercise 171 +/- 22 pg/ml). Exercise under beta-blockade is associated with an increased preload of the heart. These results further support the hypothesis that atriopeptin release during exercise is under the control of atrial stretch. The higher plasma atriopeptin concentration observed during exercise under beta-blockade may contribute to the reduction of the response of plasma renin activity (1.0 +/- 0.1 vs. 3.0 +/- 0.6 ng.ml-1.h-1) and aldosterone concentration (87 +/- 36 vs. 138 +/- 25 pg/ml). Vasopressin concentration was lower at rest and during exercise under propranolol (3.5 +/- 1.3 vs. 4.9 +/- 0.9 and 6.1 +/- 2.2 vs. 9.9 +/- 1.5 pg/ml, respectively), which might reflect a dissociation between activity of the renin-angiotensin system and vasopressin release.

Adrenergic beta-Antagonists↗

PubMed1989

Oxidation of a glucose polymer during exercise: comparison with glucose and fructose.

The purpose of this study was to compare the oxidation of 13C-labeled glucose, fructose, and glucose polymer ingested (1.33 g.kg-1 in 19 ml.kg-1 water) during cycle exercise (120 min, 53 +/- 2% maximal O2 uptake) in six healthy male subjects. Oxidation of exogenous glucose and glucose polymer (72 +/- 15 and 65 +/- 18%, respectively, of the 98.9 +/- 4.7 g ingested) was similar and significantly greater than exogenous fructose oxidation (54 +/- 13%). A transient rise in plasma glucose concentration was observed with glucose ingestion only. However, plasma insulin levels were similar with glucose and glucose polymer ingestions and significantly higher than with water or fructose ingestion. Plasma free fatty acid and glycerol responses to exercise were blunted with carbohydrate ingestion. However, fat utilization was not significantly different with water (82 +/- 14 g), glucose (60 +/- 3 g), fructose (59 +/- 11 g), or glucose polymer ingestion (60 +/- 8 g). Endogenous carbohydrate utilization was significantly lower with glucose (184 +/- 22 g), glucose polymer (187 +/- 31 g), and fructose (211 +/- 18 g) than with water (239 +/- 30 g) ingestion. Plasma volume slightly increased with water ingestion (7.4 +/- 4.5%), but the decrease was similar with glucose (-7.6 +/- 5.1%) and glucose polymer (-8.2 +/- 4.6%), suggesting that the rate of water delivery to plasma was similar with the two carbohydrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Plasma atrial natriuretic peptide during brief upright and supine exercise in humans.

The factors associated with the exercise-induced increase in plasma atrial natriuretic peptide (ANP) have not been clearly established. Thus the purpose of the study was to further document the stimulus for the exercise-induced release of ANP and to examine the role of ANP in the control of hydromineral balance during exercise. Eight healthy male volunteers (25.1 +/- 4.5 yr) were submitted to a graded cycling exercise in both the upright and supine positions. Venous blood was sampled at rest and at the end of each 5-min work load at 40, 60, and 80% maximal oxygen uptake (Vo2max), at maximal exercise, and during recovery through an indwelling catheter for the determination of plasma vasopressin, aldosterone, catecholamines, plasma renin activity, and ANP concentrations. Results indicate a significant increase in ANP (pg/ml) from rest to maximal exercise in the upright position [rest, 21.9 +/- 10.2; 40%, 24.7 +/- 12.6; 60%, 32.4 +/- 17*; 80%, 47.8 +/- 27.7*; 100% Vo2max, 65.9 +/- 34.5* (*P less than or equal to 0.05)]. Supine concentrations were significantly higher than upright at 40 (37.9 +/- 15.2), 60 (54.0 +/- 18.8), and 80% Vo2max (68.9 +/- 16.6). Plasma ANP during maximal exercise was similar in both positions. Plasma vasopressin, aldosterone, renin activity, and catecholamines increased with increasing exercise intensity in both positions, although lower values were systematically observed in the supine position. The association of higher plasma ANP and blunted plasma vasopressin, plasma renin activity, and norepinephrine concentrations during supine exercise suggests that ANP may exert modulatory effects on the control of the hydromineral hormonal system during exercise.

Adult↗

PubMed1988

Failure to alter sympathoadrenal response to psychosocial stress following aerobic training.

This experiment assessed the impact of aerobic training on sympathoadrenal, heart rate and subjective responses to psychosocial stress. Subjects were six previously sedentary males who demonstrated marked improvement in fitness level following 10 weeks of training. Plasma samples, heart rate and subjective arousal ratings were obtained prior to, during, and following exposure to stressful mental tasks within a laboratory session. With the exception of training-related bradycardia which was manifest throughout the session, no changes in plasma epinephrine and norepinephrine concentrations, heart rate or subjective reactivity or recovery were seen. These findings are inconsistent with the hypothesized beneficial effects of aerobic training on stress-response. Methodological factors such as self-selection inherent in previous correlation work or the duration of the training program should be considered in this context. The potential contribution of training-related bradycardia to enhanced coping with challenging situations is explored.

Adult↗

PubMed1988

Sympatho-endocrine and metabolic responses to exercise under post-ganglionic blockade in rats.

The purpose of this study was to further document the role of locally released norepinephrine (NE) in the control of metabolic and endocrine responses to exercise in rats. Post-ganglionic blockade with bretylium (20 mg.kg-1, i.v.) reduced NE release from sympathetic nerve endings and triggered a compensatory increase in epinephrine (E) release from the adrenal medulla, as reflected by plasma NE and E concentrations at rest and exercise (E/NE ratio = 2.92 +/- 0.53 and 2.48 +/- 0.51 vs 0.62 +/- 0.15 and 1.48 +/- 0.18 in control rats; mean +/- SE). Following bretylium administration a reduction in running time to exhaustion (28 m.min-1, 8% slope: 33 +/- 2 min vs 74 +/- 10 min) was associated with 1) a faster decrease in blood glucose concentration (3.58 +/- 0.80 mM vs 8.09 +/- 0.38 mM in control rats exercised for 33 min); and 2) an increased glycogen store utilization in fast-twitch muscles (superficial vastus lateralis and gastrocnemius lateralis). Glycogen utilization was not modified in soleus muscle and in the liver. Taken together these results suggest that post-ganglionic blockade increased carbohydrate store and peripheral blood glucose utilization. This could reflect an impairment in fat mobilization and utilization which might be secondary to a reduction of NE release in the adipose tissue and/or in the endocrine pancreas.

Animals↗