The effect of exercise on the clearance of infused acetate in the horse (original) (raw)
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Distribution of lactate in plasma and erythrocytes during and after exercise in horses
The British veterinary journal
The distribution of lactate between red blood cells (RBC) and plasma was examined at rest, during exercise and 30 min after exercise in six Standardbred horses. Lactate and water concentrations were measured in blood and plasma samples collected prior to exercise, during the last 15 s of each step of an incremental exercise test and at 5 min intervals during the first 30 min after exercise. The mean ratio of RBC lactate concentration (RBCLa) to plasma lactate concentration (PLa) prior to exercise was 1.02 +/- 0.34. Haemoconcentration during exercise was associated with more rapid accumulation of lactate in plasma than in RBCs. Mean whole blood lactate concentration (BLa) was only 59% of PLa in samples collected during exercise. BLa was highly correlated with PLa during exercise (r = 0.98; P < 0.001), but individual PLa values differed from predicted BLa values by up to 2.1 mmol l-1 when PLa exceeded 8 mmol l-1. At each exercise speed and time after exercise there was a large vari...
Journal of applied physiology (Bethesda, Md. : 1985), 2000
We examined the effects of increased glucose availability on glucose kinetics and substrate utilization in horses during exercise. Six conditioned horses ran on a treadmill for 90 min at 34 +/- 1% of maximum oxygen uptake. In one trial [glucose (Glu)], glucose was infused at a mean rate of 34.9 +/- 1.1 micromol. kg(-1). min(-1), whereas in the other trial [control (Con)] an equivalent volume of isotonic saline was infused. Plasma glucose increased during exercise in Glu (90 min: 8.3 +/- 1.7 mM) but was largely unchanged in Con (90 min: 5.1 +/- 0.4 mM). In Con, hepatic glucose production (HGP) increased during exercise, reaching a peak of 38.6 +/- 2.7 micromol. kg(-1). min(-1) after 90 min. Glucose infusion partially suppressed (P < 0.05) the rise in HGP (peak value 25.8 +/- 3.3 micromol. kg(-1). min(-1)). In Con, glucose rate of disappearance (R(d)) rose to a peak of 40.4 +/- 2.9 micromol. kg(-1). min(-1) after 90 min; in Glu, augmented glucose utilization was reflected by values...
Low dose of dichloroacetate infusion reduces blood lactate after submaximal exercise in horses
Pesquisa Veterinária Brasileira, 2013
Pesq. Vet. Bras. 33(1):57-60, janeiro 2013 57 RESUMO.-[Baixa dose de infusão de dicloroacetato reduz o lactato sanguíneo após exercício submáximo em cavalos.] A administração aguda de um ativador indireto da enzima piruvato desidrogenase (PD) em atletas da espécie humana provoca redução na concentração de lactato sanguíneo durante e após exercício. Uma dose única, intravenosa de 2.5m.kg -1 de dicloroacetato (DCA) foi administrada antes de um exercício teste incremental submáximo . 2013. Low dose of dichloroacetate infusion reduces blood lactate after submaximal exercise in horses. Pesquisa Veterinária Brasileira 33 :57-60. The acute administration of an indirect activator of the enzyme pyruvate dehydrogenase (PDH) in human athletes causes a reduction in blood lactate level during and after exercise. A single IV dose (2.5m.kg -1 ) of dichloroacetate (DCA) was administered before a submaximal incremental exercise test (IET) with five velocity steps, from 5.0 m.s -1 for 1 min to 6.0, 6.5, 7.0 and 7.5m.s -1 every 30s in four untrained mares. The blood collections were done in the period after exercise, at times 1, 3, 5, 10, 15 and 20 min. Blood lactate and glucose (mM) were determined electro-enzymatically utilizing a YSI 2300 automated analyzer. There was a 15.3% decrease in mean total blood lactate determined from the values obtained at all assessment times in both trials after the exercise. There was a decrease in blood lactate 1, 3, 5, 10, 15 and 20 min after exercise for the mares that received prior DCA treatment, with respective mean values of 6.31±0.90 vs 5.81±0.50, 6.45±1.19 vs 5.58±1.06, 6.07±1.56 vs 5.26±1.12, 4.88±1.61 vs 3.95±1.00, 3.66±1.41 vs 2.86±0.75 and 2.75±0.51 vs 2.04±0.30. There was no difference in glucose concentrations. By means of linear regression analysis, V 140 , V 160 , V 180 and V 200 were determined (velocity at which the rate heart is 140, 160, 180, and 200 beats/minute, respectively). The velocities related to heart rate did not differ, indicating that there was no ergogenic effect, but prior administration of a relatively low dose of DCA in mares reduced lactatemia after an IET.
2010
The time course of insulin sensitivity, skeletal muscle glycogen and GLUT4 content, and glycogen synthase (GS) activity after a single bout of intense exercise was examined in eight horses. On separate days, a euglycemic-hyperinsulinemic clamp (EHC) was undertaken at 0.5, 4, or 24 h after exercise or after 48 h of rest [control (Con)]. There was no increase in mean glucose infusion rate (GIR) with exercise (0.5-, 4-, and 24-h trials), and GIR was significantly decreased at 0.5 h postexercise (GIR: 8.6 Ϯ 2.7, 6.7 Ϯ 2.0, 9.0 Ϯ 2.0, and 10.6 Ϯ 2.2 mg ⅐ kg Ϫ1 ⅐ min Ϫ1 for Con and at 0.5, 4, and 24 h, respectively). Before each EHC, muscle glycogen content (mmol glucosyl units/kg dry muscle) was higher (P Ͻ 0.05) for Con (565 Ϯ 102) than for other treatments (317 Ϯ 84, 362 Ϯ 79, and 382 Ϯ 74 for 0.5, 4, and 24 h, respectively) and muscle GLUT4 content was unchanged. Pre-EHC active-to-total GS activity ratio was higher (P Ͻ 0.05) at 0.5, 4, and 24 h after exercise than in Con. Post-EHC active GS and GS activity ratio were higher (P Ͻ 0.05) in Con and at 24 h. There was a significant inverse correlation (r ϭ Ϫ0.43, P ϭ 0.02) between glycogen content and GS activity ratio but no relationship between GS activity and GIR. The lack of increase in insulin sensitivity, determined by EHC, after exercise that resulted in a significant reduction in muscle glycogen content is consistent with the slow rate of muscle glycogen resynthesis observed in equine studies.
Blood lactate threshold reflects glucose responses in horses submitted to incremental exercise test
Arquivo Brasileiro de Medicina Veterinária e Zootecnia, 2008
The energy necessary for muscle contraction is obtained from the hydrolysis of ATP, releasing inorganic phosphate. ATP can be furnished by phosphocreatine, glucose, glycogen, amino acids and free fatty acids. The production of ATP is much more efficient in the presence of oxygen than in its absence. The anaerobic metabolism of glucose, although less efficient than the aerobic, represents an important and rapid mechanism of energy generation. Several factors regulate the activity of the glycolytic pathway, such as the availability of oxygen, lactate dehydrogenase (LDH) activity and the ATP/ADP ratio. As this ratio decreases the anaerobic glycolysis is stimulated, increasing the production of pyruvate and lactate.
Substrate use in horses during exercise - the ‘fasted’ compared to the postprandial state
Vlaams Diergeneeskundig Tijdschrift
Training in the fasted state has beneficial effects on performance in the human athlete. In the horse, training in the fasted state is associated with an increased mobilization of non-esterified fatty acids (NEFA) as an energy source. This is in contrast with postprandial (grain-fed) training, during which lipolysis is suppressed. A higher NEFA availability is thought to reduce muscle glycogen depletion and muscle acidification. This could aid in delaying muscle fatigue. The equine gastrointestinal tract and roughage rich diet do not allow a real ‘fasted’ state. Luckily, roughage does not induce high plasma insulin peaks, and therefore does not have the same negative effects as grain feeding. Furthermore, the roughage-containing hindgut serves as a fluid and electrolyte buffer and continuously provides the liver with propionic acid, a precursor used in gluconeogenesis. In horses, unlike in human athletes, there is still a lot to discover when it comes to optimal pre-exercise feeding...
Journal of Equine Veterinary Science, 2014
Modifications of some serum electrolyte concentration during two international *** show jumping competition performed in two consecutive weekends were evaluated. Serum sodium (Na), chloride (Cl), magnesium (Mg), potassium (K), phosphorous (P), calcium (Ca), iron (Fe), and blood lactate on 14 well-trained Italian saddle horses were assessed. Blood samples were collected before the beginning of the competition (T0B), within 10 minutes after the end of race (R1, R2, and R3), and on the day after competition (T0R). The same procedure was followed on the second weekend (R4, R5, R6, and T1R). One-way repeated measures analysis of variance was applied on collected data, and a significant effect on sampling time (P < .05) on all parameters studied was found. These results suggest that serum electrolytes and blood lactate concentration are responsive to intense exercise and could be considered an important factor for a correct management training's planning.