Ole Bækgaard Nielsen

Effects of extracellular HCO3¯ on fatigue, pHi, and K+ efflux in rat skeletal muscles

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Effects of extracellular HCO3¯ on fatigue, pHi, and K+ efflux in rat skeletal muscles. / Broch-Lips, Martin; Overgaard, Kristian; Praetorius, Helle A.; Nielsen, Ole Bækgaard.

In: Journal of Applied Physiology, Vol. 103, No. 2, 01.08.2007, p. 494-503.

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@article{306674b522e84955bd34d7621a657168,
title = "Effects of extracellular HCO3¯ on fatigue, pHi, and K+ efflux in rat skeletal muscles",
abstract = "Elevated plasma HCO3 - can improve exercise endurance in humans. This effect has been related to attenuation of the work-induced reduction in muscle pH, which is suggested to improve performance via at least two mechanisms: 1) less inhibition of muscle enzymes and 2) reduced opening of muscle KATP channels with less ensuing reduction in excitability. Aiming at determining whether the ergogenic effect of HCO3 - is related to effects on muscles, we examined the effect of elevating extracellular HCO3 - from 25 to 40 mM (pH from 7.4 to 7.6) on fatigue, intracellular pH (pHi), and K+ efflux in isolated rat skeletal muscles contracting isometrically. Fatigue induced by 30-Hz stimulation at 30 and 37°C was similar between soleus muscles incubated in high and normal HCO3 - concentrations. In extensor digitorum longus muscles stimulated at 60 Hz, elevated HCO 3 - did not affect fatigue at 30°C. In soleus muscles, 30-Hz stimulation induced a ∼0.2 unit reduction in pHi, as determined by using the pH-sensitive probe 2′,7′-bis(2-carboxyethyl)-5(6)- carboxyfluorescein. This reduction in pHi was not affected by elevated HCO 3 -. Estimation of K+ efflux using 86Rb+ showed that elevated HCO3 - did not affect K+ efflux at rest or during contractions. Similarly, other modifications of the intraand extracellular pH had little effect on K + efflux during contraction. In conclusion, elevated extracellular HCO3 - had no significant effect on muscle fatigue, pH i, and K+ efflux. These findings indicate that alternative mechanisms must be considered for the ergogenic effect of HCO3 - observed in integral exercise studies.",
keywords = "Muscle fatigue",
author = "Martin Broch-Lips and Kristian Overgaard and Praetorius, {Helle A.} and Nielsen, {Ole B{\ae}kgaard}",
year = "2007",
month = aug,
day = "1",
doi = "10.1152/japplphysiol.00049.2007",
language = "English",
volume = "103",
pages = "494--503",
journal = "Journal of Applied Physiology",
issn = "8750-7587",
publisher = "AMER PHYSIOLOGICAL SOC",
number = "2",

}

RIS

TY - JOUR

T1 - Effects of extracellular HCO3¯ on fatigue, pHi, and K+ efflux in rat skeletal muscles

AU - Broch-Lips, Martin

AU - Overgaard, Kristian

AU - Praetorius, Helle A.

AU - Nielsen, Ole Bækgaard

PY - 2007/8/1

Y1 - 2007/8/1

N2 - Elevated plasma HCO3 - can improve exercise endurance in humans. This effect has been related to attenuation of the work-induced reduction in muscle pH, which is suggested to improve performance via at least two mechanisms: 1) less inhibition of muscle enzymes and 2) reduced opening of muscle KATP channels with less ensuing reduction in excitability. Aiming at determining whether the ergogenic effect of HCO3 - is related to effects on muscles, we examined the effect of elevating extracellular HCO3 - from 25 to 40 mM (pH from 7.4 to 7.6) on fatigue, intracellular pH (pHi), and K+ efflux in isolated rat skeletal muscles contracting isometrically. Fatigue induced by 30-Hz stimulation at 30 and 37°C was similar between soleus muscles incubated in high and normal HCO3 - concentrations. In extensor digitorum longus muscles stimulated at 60 Hz, elevated HCO 3 - did not affect fatigue at 30°C. In soleus muscles, 30-Hz stimulation induced a ∼0.2 unit reduction in pHi, as determined by using the pH-sensitive probe 2′,7′-bis(2-carboxyethyl)-5(6)- carboxyfluorescein. This reduction in pHi was not affected by elevated HCO 3 -. Estimation of K+ efflux using 86Rb+ showed that elevated HCO3 - did not affect K+ efflux at rest or during contractions. Similarly, other modifications of the intraand extracellular pH had little effect on K + efflux during contraction. In conclusion, elevated extracellular HCO3 - had no significant effect on muscle fatigue, pH i, and K+ efflux. These findings indicate that alternative mechanisms must be considered for the ergogenic effect of HCO3 - observed in integral exercise studies.

AB - Elevated plasma HCO3 - can improve exercise endurance in humans. This effect has been related to attenuation of the work-induced reduction in muscle pH, which is suggested to improve performance via at least two mechanisms: 1) less inhibition of muscle enzymes and 2) reduced opening of muscle KATP channels with less ensuing reduction in excitability. Aiming at determining whether the ergogenic effect of HCO3 - is related to effects on muscles, we examined the effect of elevating extracellular HCO3 - from 25 to 40 mM (pH from 7.4 to 7.6) on fatigue, intracellular pH (pHi), and K+ efflux in isolated rat skeletal muscles contracting isometrically. Fatigue induced by 30-Hz stimulation at 30 and 37°C was similar between soleus muscles incubated in high and normal HCO3 - concentrations. In extensor digitorum longus muscles stimulated at 60 Hz, elevated HCO 3 - did not affect fatigue at 30°C. In soleus muscles, 30-Hz stimulation induced a ∼0.2 unit reduction in pHi, as determined by using the pH-sensitive probe 2′,7′-bis(2-carboxyethyl)-5(6)- carboxyfluorescein. This reduction in pHi was not affected by elevated HCO 3 -. Estimation of K+ efflux using 86Rb+ showed that elevated HCO3 - did not affect K+ efflux at rest or during contractions. Similarly, other modifications of the intraand extracellular pH had little effect on K + efflux during contraction. In conclusion, elevated extracellular HCO3 - had no significant effect on muscle fatigue, pH i, and K+ efflux. These findings indicate that alternative mechanisms must be considered for the ergogenic effect of HCO3 - observed in integral exercise studies.

KW - Muscle fatigue

UR - http://www.scopus.com/inward/record.url?scp=34547635955&partnerID=8YFLogxK

U2 - 10.1152/japplphysiol.00049.2007

DO - 10.1152/japplphysiol.00049.2007

M3 - Journal article

C2 - 17446415

AN - SCOPUS:34547635955

VL - 103

SP - 494

EP - 503

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

SN - 8750-7587

IS - 2

ER -