Cyclical plasma electrolyte and acid–base responses to meal feeding in horses over a 24-h period

Waller, Amanda P.; Smithurst, Kerri Jo; Ecker, Gayle L.; Geor, R. J.; Lindinger, Michael I.

doi:10.1079/ecp200559

Cited by 10 publications

(7 citation statements)

References 14 publications

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“…This is in large part due to the large distribution volume for supplemented electrolytes, comprising c. 100 l of extracellular fluid and 200 l of intracellular fluid. The increase in plasma [Na þ ] during early recovery in both trials coincided with increases in [PP] and Hct, and thus is likely a result of a cyclical fluid shift between the plasma compartment and the gastrointestinal tract as a result of feeding 19 . The decrease in plasma [K þ ] during early recovery has been demonstrated previously after moderate-4 and high-intensity exercise 2 , and can be explained by high rates of Na þ /K þ -ATPase activity in previously contracting muscles 20 .…”

Section: Independent Variablesmentioning

confidence: 87%

Electrolyte supplementation after prolonged moderate-intensity exercise results in decreased plasma [TCO₂] in Standardbreds

Waller

Heigenhauser

Lindinger

2007

Equine Comp. Exerc. Physiol.

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Link to this article: http://journals.cambridge.org/abstract_S1478061507890086How to cite this article: Amanda Waller, George J Heigenhauser and Michael I Lindinger (2007). Electrolyte supplementation after prolonged moderate-intensity exercise results in decreased plasma [TCO2] in Standardbreds. Equine and Comparative Exercise Physiology, 4, pp 149-158 AbstractThe present study used the physicochemical approach to characterize the changes in acid-base status that occur in Standardbreds after post-exercise electrolyte supplementation. Jugular venous blood was sampled from six conditioned Standardbreds on two separate occasions, at rest and for 24 h following a competitive exercise test (CET) designed to simulate the speed and endurance test of a 3-day event. After the CETs, horses were given water ad libitum and either a hypotonic commercial electrolyte solution, via nasogastric tube followed by a typical hay/grain meal, or a hay/grain meal alone. The electrolyte supplementation resulted in c. 2 mmol l 21 decreased plasma [TCO 2 ] during the recovery period as compared with control. The primary contributor to the decreased [TCO 2 ] with electrolyte supplementation was a decreased strong ion difference ([SID]), as a result of the non-significant increase in plasma [Cl 2 ]. Additionally, electrolyte supplementation resulted in faster restoration of hydration status compared with control, as evidenced by faster recovery of plasma [protein] and total weak acid concentration ([A tot ]). It is concluded that oral administration of a hypotonic electrolyte solution after prolonged moderate-intensity exercise diminishes the post-exercise alkalosis, and that recovery of hydration status is still incomplete 24 h after exercise when no electrolytes are given. Thus, supplementation with electrolytes according to estimated sweat losses may attenuate post-exercise increases in plasma [TCO 2 ], which is of significant practical interest to the horse racing community, as a testing threshold of greater than 37 mmol l 21 is used by many racing jurisdictions to determine whether a horse has been administered an alkalinizing agent.

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Section: Independent Variablesmentioning

confidence: 87%

Electrolyte supplementation after prolonged moderate-intensity exercise results in decreased plasma [TCO₂] in Standardbreds

Waller

Heigenhauser

Lindinger

2007

Equine Comp. Exerc. Physiol.

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“…Intestinal absorption of Na + and K + at rest Horses were fasted overnight and water was removed 3 h prior to the start of the trials in order to avoid confounding influences of feeding on measured plasma variables (Waller et al 2005). All studies were performed during the same time of the morning in order to avoid the confounding influences of diurnal variation on measured variables (Waller et al 2005). Three of the six horses were used for the Na + trial and the other three horses were used for the K + trial, and only one horse was studied on a given day.…”

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confidence: 99%

Gastric emptying, intestinal absorption of electrolytes and exercise performance in electrolyte‐supplemented horses

Lindinger

Ecker

2012

Experimental Physiology

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Horses lose considerably more electrolytes through sweating during prolonged exercise than can be readily replaced through feeds. The present study tested an oral electrolyte supplement (ES) designed to replace sweat electrolyte losses. We measured gastric emptying of 3 litres of ES (using gamma imaging of (99)Tc-sulfide colloid), the absorption of Na(+) and K(+) from the gastrointestinal tract using (24)Na(+) and (42)K(+), and the distribution of these ions in the body by measuring radioactivity within plasma and sweat during exercise. Three litres of ES emptied from the stomach as fast as water, with a half-time of 47 min, and appeared in plasma by 10 min after administration (n = 4 horses). Peak values of plasma (24)Na(+) and (42)K(+) radioactivity occurred at 20-40 min, and a more rapid disappearance of K(+) radioactivity from plasma was indicative of movement of K(+) into cells (n = 3 horses). In a randomized crossover experiment (n = 4 horses), 1 h after administration of placebo (water), 1 or 3 litres of ES containing (24)Na(+), horses exercised on a treadmill at 30% of peak oxygen uptake until voluntary fatigue. The (24)Na(+) appeared in sweat at 10 min of exercise, and when horses received 3 litres of ES the duration to voluntary fatigue was increased in all horses by 33 ± 10%. It is concluded that an oral ES designed to replace sweat ion losses was rapidly emptied from the gastrointestinal tract, rapidly absorbed in the upper intestinal tract and rapidly distributed within the body. The ES clearly served as a reservoir to replace sweat ion losses during exercise, and administration of ES prior to exercise resulted in increased duration of submaximal exercise.

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“…However, the changes in [H þ ], TCO 2 and the independent variables were relatively small compared to those seen with exercise 20,21 and feeding 8 2 . The amplitude of change in plasma TCO 2 was 5-10 meq l 21 during the sampling period, and some horses naturally exhibited TCO 2 levels of 35-37 meq l 21 at several time points throughout the day.…”

Section: Dependent Variablesmentioning

confidence: 76%

“…The same batches of hay and grain were fed during both trials. A detailed nutritional analysis of the diet has been published in a companion paper 8 . The horses were fed daily at 8 am and 7 pm.…”

Section: Dietmentioning

confidence: 99%

“…This nocturnal increase in [K þ ] has been demonstrated previously 1,6,11 and is thought to be associated with a decreased activity of cellular Na K pumps during night-time resting periods 12 . A major cofounder of the previous studies of plasma [K þ ] variation in horses is that all animals were fed at some point during the sampling period as plasma [K þ ] is affected by feeding 3,8,13 . However, in a companion study to the present one, blood samples were taken from the same two groups of horses on days when the horses were fed normally (see Waller et al 8 ) and a decrease in plasma [K þ ] was still demonstrated during the daytime, demonstrating that plasma [K þ ] does exhibit diurnal variation.…”

Section: Independent Variablesmentioning

confidence: 99%

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Daily variation in plasma electrolyte and acid–base status in fasted horses over a 25 h period of rest

Waller

Smithurst

Ecker

et al. 2006

Equine Comp. Exerc. Physiol.

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I Lindinger (2006). Daily variation in plasma electrolyte and acid-base status in fasted horses over a 25 h period of rest. Equine and Comparative Exercise Physiology, 3, pp 29-36Abstract Measurement and interpretation of acid-base status are important in clinical practice and among racing jurisdictions to determine if horses have been administered alkalinizing substances for the purpose of enhancing performance. The present study used the physicochemical approach to characterize the daily variation in plasma electrolytes and acid-base state that occurs in horses in the absence of feeding and exercise. Jugular venous blood was sampled every 1-2 h from two groups (n ¼ 4 and n ¼ 5) of Standardbred horses over a 25 h period where food and exercise were withheld. One group of horses was studied in October and one in December. The time course and magnitude of circadian responses differed between the two groups, suggesting that subtle differences in environment may manifest in acid-base status. Significant daily variation occurred in plasma weak acid concentration ([A tot ]) and strong ion difference ([SID]), [Cl 2 ], [K þ ], [Na þ ] and [lactate 2 ], which contributed to significant changes in [H þ ] and TCO 2 . The night-time period was associated with a mild acidosis, marked by increases in plasma [H þ ] and decreases in TCO 2 , compared with the morning hours. The night-time acidosis resulted from an increased plasma [A tot ] due to an increased plasma protein concentration ([PP]), and a decreased [SID] due to increases in [Cl 2 ] and decreases in [Na þ ]. An increased plasma [K þ ] during the night-time had a mild alkalotic effect. There were no differences in pCO 2 . It was concluded that many equine plasma electrolyte and acid-base parameters exhibit fluctuations in the absence of feeding and exercise, and it is likely that some of these changes are due to daily variation.

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Cyclical plasma electrolyte and acid–base responses to meal feeding in horses over a 24-h period

Cited by 10 publications

References 14 publications

Electrolyte supplementation after prolonged moderate-intensity exercise results in decreased plasma [TCO₂] in Standardbreds

Electrolyte supplementation after prolonged moderate-intensity exercise results in decreased plasma [TCO₂] in Standardbreds

Gastric emptying, intestinal absorption of electrolytes and exercise performance in electrolyte‐supplemented horses

Daily variation in plasma electrolyte and acid–base status in fasted horses over a 25 h period of rest

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