Elevated muscle citrate does not reduce carbohydrate utilization during tetanic stimulation

1994 ◽  
Vol 72 (2) ◽  
pp. 117-125 ◽  
Author(s):  
David J. Dyck ◽  
Lawrence L. Spriet
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Hind Limb ◽  
Tetanic Stimulation ◽  
Phosphate Content ◽  
Carbohydrate Utilization ◽  
Rest Perfusion ◽  
Glycogen Utilization ◽  
White Gastrocnemius ◽  
Intense Stimulation

The purposes of this study were to determine whether enhanced free fatty acid delivery would result in increased muscle citrate levels and to establish whether the effects of this putative phosphofructokinase inhibitor would be manifested during intense stimulation demanding glycogen as a fuel. Hind-limb muscles were perfused with either no or high (0.93 ± 0.03 mM) free fatty acids for 10 min at rest, and during 5 min of tetanic stimulation. Muscles sampled at the end of the rest perfusion or stimulation were soleus (slow oxidative), red gastrocnemius (fast oxidative glycolytic), and white gastrocnemius (fast glycolytic). Muscle citrate content was unaffected during rest perfusion with no free fatty acids, whereas high free fatty acids significantly elevated citrate above control in soleus, red gastrocnemius, and white gastrocnemius (by 0.39 ± 0.13, 0.53 ± 0.10, and 0.29 ± 0.07 μmol∙g−1 dry muscle, respectively). Following 1 min of stimulation, citrate content in soleus and red gastrocnemius was not different from control in the absence of free fatty acids but accumulated significantly with high free fatty acids (0.26 ± 0.05 and 0.28 ± 0.04 μmol∙g−1 dry muscle, respectively). Following 5 min of stimulation, soleus and red gastrocnemius citrate content decreased with no free fatty acids but increased significantly with high free fatty acids (0.42 ± 0.10 μmol∙g−1 dry muscle) in soleus and remained unchanged in red gastrocnemius. The presence of high free fatty acids had no effect on glycogen utilization or lactate accumulation in stimulated soleus and red gastrocnemius, or stimulated white gastrocnemius citrate, glycogen, or lactate contents. In addition, no effect of elevated free fatty acids on resting or stimulated muscle glucose-6-phosphate content, glucose uptake, or lactate efflux was observed. In conclusion, the elevation of muscle citrate due to the presence of free fatty acids in the perfusate did not reduce muscle glycogenolysis when the demand for energy was great.Key words: citrate glycolysis, phosphofructokinase, glycogen.

EFFECT OF COLD EXPOSURE ON RESPIRATORY C14O2 PRODUCTION DURING INFUSION OF ALBUMIN-BOUND PALMITATE-1-C14 IN WHITE RATS

1961 ◽  
Vol 39 (2) ◽  
pp. 219-224 ◽  
Author(s):  
Roberto Masironi ◽  
Florent Depocas
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Cold Exposure ◽  
Carbohydrate Utilization ◽  
White Rats ◽  
Constant Rate ◽  
Oxidation Of Glucose ◽  
Fasted Rats

Albumin palmitate-1-C14 complex was infused at a constant rate through a carotid cannula (inserted 5–7 days earlier) into otherwise intact non-fasted rats in environments at 30° or 6 °C, after acclimation to 30° or 6 °C. At 6 °C, both warm- and cold-acclimated rats similarly exhaled as CI4O2 a larger proportion of the injected C14 and gave lower terminal amounts of C14 in the extracted free fatty acids (F.F.A.) of plasma than at 30 °C. These results indicate that plasma F.F.A. serve as substrate for cold-thermogenesis. Also, increased turnover and oxidation of F.F.A. are not always inversely related to carbohydrate utilization but may be increased under conditions which result in concomitantly higher rates of turnover and oxidation of glucose.

High physiological levels of epinephrine do not enhance muscle glycogenolysis during tetanic stimulation

1994 ◽  
Vol 77 (2) ◽  
pp. 956-962 ◽  
Author(s):  
A. Chesley ◽  
D. J. Dyck ◽  
L. L. Spriet
Keyword(s):  
Tetanic Stimulation ◽  
Control Groups ◽  
Perfusion Medium ◽  
Short Term ◽  
Muscle Lactate ◽  
Rest Perfusion ◽  
Train Duration ◽  
Fast Twitch ◽  
And Control ◽  
White Gastrocnemius

This study examined whether high physiological concentrations of epinephrine (EPI) would enhance muscle glycogenolysis during intense muscular contractions. Muscles of the rat hindlimb were perfused for 12 min at rest and 45 s of tetanic stimulation (1.0-Hz train rate, 100-ms train duration at 80 Hz) without EPI (control) or with 15 or 35 nM EPI. In the EPI groups the muscles were perfused with EPI for the last 2 min of rest perfusion and throughout stimulation. Glycogenolysis in the white gastrocnemius, red gastrocnemius, plantaris, and soleus muscles during stimulation was unaffected by the presence of EPI in the perfusion medium. In addition, muscle lactate and hindlimb lactate efflux were similar in EPI and control groups. It is concluded that EPI is not important for enhancing glycogenolysis in rat muscles composed predominantly of fast-twitch fibers during intense short-term tetanic stimulation.

Sparing effect of chronic high-altitude exposure on muscle glycogen utilization

1982 ◽  
Vol 52 (4) ◽  
pp. 857-862 ◽  
Author(s):  
A. J. Young ◽  
W. J. Evans ◽  
A. Cymerman ◽  
K. B. Pandolf ◽  
J. J. Knapik ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
High Altitude ◽  
Muscle Glycogen ◽  
Vastus Lateralis ◽  
Venous Blood ◽  
Vastus Lateralis Muscle ◽  
Before And After ◽  
Glycogen Utilization ◽  
Sparing Effect

Substrate utilization during heavy [approximately 85% maximum O2 consumption (VO2max)] bicycle exercise was examined in eight low-altitude residents at sea level (SL) and after acute (2 h) and chronic (18 days) high-altitude (HA) exposure at 4,300 m. Mean VO2max was approximately 27% lower at acute HA than at SL and did not change significantly with continued HA exposure. Biopsies from the vastus lateralis muscle and venous blood samples were obtained before and after 30 min of exercise, whereas determinations of the respiratory exchange ratio (R) were made at 10-min intervals during each of the submaximal bouts. Resting levels of serum-free fatty acids at acute and chronic HA were, respectively, two and three times higher than SL but were unchanged with exercise. Exercise did not alter resting serum glycerol levels at SL or during acute HA, but during chronic HA resting glycerol levels were increased 11-fold. Although mean blood lactate concentrations following exercise at SL and acute HA were not significantly different, postexercise lactate concentrations were 87% lower after chronic HA. During exercise at SL and acute HA, muscle glycogen utilization and R were not different. At chronic HA, muscle glycogen utilization and R were 41 and 15% lower, respectively. These data suggest that after chronic HA exposure, increased mobilization and use of free fatty acids during exercise resulted in sparing of muscle glycogen.

scholarly journals THE EFFECTS OF EUGLVCEMIC INSULIN CLAMP ON THE METABOLISM OF 3-HYDROXVBUTYRATE AND PLASMA FREE FAHY ACIDS BY THE HIND LIMB OF LACRATING SHEEP

2021 ◽  
Vol 15 ◽  
pp. 63-69
Author(s):  
A. J. A OSUAGWUH ◽  
R. R. SMITHARD ◽  
J. METCALFE ◽  
T. E. C. WEEKES
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Hind Limb ◽  
Plasma Insulin ◽  
Extraction Ratio ◽  
Similar Relationship ◽  
Exogenous Insulin ◽  
Plasma Free Fatty Acids ◽  
Arterial Concentration ◽  
Plasma Insulin Levels

The effects of exogenous insulin, with euglycemia, on the concentration differences, extraction ratio and uptake of 3- hydroxybutyrate and plasma free fatty acids by the lactating sheep hind limb were studied. Generally, the results showed that with increasing plasma insulin levels, while maintaining euglycemia, the concentrations, arterio-venous concentration differences, extraction ratio and uptake of 3-hydrubutyrate and free fatty acids Were significantly (P<0.05) reduced, but Significant correlation was established between arterial concentration of 3-hydtoxvbutyrate and plasma free fatty acids and their uptake. A similar relationship was also obtained between the arterial concentrations of 3-hydroxybutyrate plasma free fatty acids.

Effect of high FFA on glycogenolysis in oxidative rat hindlimb muscles during twitch stimulation

1996 ◽  
Vol 270 (4) ◽  
pp. R766-R776 ◽  
Author(s):  
D. J. Dyck ◽  
S. J. Peters ◽  
P. S. Wendling ◽  
L. L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acids ◽  
Free Fatty Acids ◽  
Glucose Uptake ◽  
Rat Skeletal Muscle ◽  
Acetyl Coa ◽  
Hindlimb Muscles ◽  
Rest Perfusion ◽  
Wide Range ◽  
Glycogen Sparing

The effect of elevated free fatty acids (FFA) on carbohydrate (CHO) utilization in the oxidative muscles of the isolated hindlimb was determined using twitch contraction paradigms evoking a wide range of O2 uptakes and glycogenolysis. The hindlimb was perfused with either 0 or 1.8 mM FFA for 10 min at rest and then subjected to 20 min of stimulation at 0.4, 0.7, 1, 2, 3, or 4 Hz. Soleus (Sol), plantaris (Pl), and red gastrocnemius (RG) were sampled after rest perfusion or stimulation. FFA had little effect on glycogenolysis during stimulation, although glycogen sparing occurred with one of the lesser intensity protocols in each muscle (Sol, 0.4 Hz; RG, 0.7 Hz; Pl, 1 Hz). Muscle citrate and acetyl-CoA were elevated in Sol during several stimulation protocols with high FFA, but this effect was inconsistent in Pl and RG. The sparing of glycogen, when it did occur, was generally unrelated to increases in either citrate or acetyl-CoA content. Furthermore, protocols in which citrate or acetyl-CoA were elevated in the presence of elevated FFA did not demonstrate glycogen sparing. Hindlimb lactate efflux at rest was reduced with FFA but unaffected during stimulation. Glucose uptake was unaffected by FFA at rest and during stimulation protocols, except 3 Hz. The present study does not support the classically proposed roles of citrate and acetyl-CoA in the FFA-induced downregulation of CHO utilization in electrically stimulated rat skeletal muscle.

GENERAL EFFECTS OF α-MELANOCYTE STIMULATING HORMONE IN THE RABBIT

1965 ◽  
Vol 48 (4) ◽  
pp. 609-618 ◽  
Author(s):  
H. K. Dyster-Aas ◽  
C. E. T. Krakau
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Serum Calcium ◽  
Calcium Level ◽  
Serum Calcium Level ◽  
Systemic Effects ◽  
List Type ◽  
Aqueous Flare ◽  
Melanocyte Stimulating Hormone ◽  
Blood Aqueous Barrier

ABSTRACT In addition to the previously described permeability disturbance in the blood aqueous barrier of the eye, measured as an increase of the aqueous flare, a series of transitory systemic effects have been recorded following the subcutaneous injection of synthetic α-MSH: marked increase of the free fatty acids in plasma, decrease in the serum calcium level, decrease in the blood pressure, increase in the skin temperature, increased frequency and diminished amplitude of respiration, presence of slow waves in the EEG. There is a correlation between the magnitude of the aqueous flare increase and the increase of free fatty acids in plasma and also between the aqueous flare and the minimum serum calcium level.

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