Effects of cromakalim on the membrane potassium permeability of frog skeletal muscle <i>in vitro</i>

Benton, David; Haylett, D.G.

doi:10.1111/j.1476-5381.1992.tb14478.x

Cited by 10 publications

(5 citation statements)

References 25 publications

(34 reference statements)

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“…Since APs were measured 3 min after fatigue, it then appears that glibenclamide is capable of blocking KATP channels in less than 4 min. This is in agreement with previous studies using intact frog muscle fibres in which 1-10 ,mol I-' glibenclamide blocks the KATP current activated by cromakalin and SR44866 in less than 2 min (Sauviat et al 1991;Benton & Haylett, 1992). The time course of the J. Physiol.…”

Section: Discussionsupporting

confidence: 81%

“…glibenclamide blocks the KATP current activated by cromakalin and SR44866 in less than 2 min (Sauviat et al 1991;Benton & Haylett, 1992). The time course of the glibenclamide effect in unfatigued and fatigued frog muscle fibres is, however, strikingly shorter than the effect observed in metabolically exhausted muscle fibres for which the change in membrane conductance (Fig.…”

Section: Discussionmentioning

confidence: 91%

“…The half-repolarization time and maximum rate of repolarization of muscle fibres exposed to glibenclamide during fatigue probably represents the repolarization phase of fatigued muscle fibres without the contribution of KATp channels; but more importantly without any side effect from having the KATP channels blocked at the onset of fatigue as the full effect of glibenclamide is observed in 1-2 min (Sauviat et al 1991;Benton & Haylett, 1992). In fact, blocking the KATP channels at the onset of fatigue does not affect the repolarization phase any further because no differences in half-repolarization time and maximum rate of repolarization are observed betwcen muscle fibres exposed to glibenclamide before or during fatigue.…”

Section: Discussionmentioning

confidence: 99%

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The effect of glibenclamide on frog skeletal muscle: evidence for K+ATP channel activation during fatigue.

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Comtois

Renaud

1994

The Journal of Physiology

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1. The purpose of this study was to determine whether ATP-sensitive K+ (KATP) channels are activated and contribute to the decrease in force during fatigue development in the sartorius muscle of the frog, Rana pipiens. Tetanic force (elicited by field stimulation), action potential and membrane conductance (using conventional microelectrodes), were measured in the presence and absence of glibenclamide, a KATP channel antagonist. Experiments were performed in bicarbonate-buffered solutions at pH 7-2.2. In unfatigued muscle 100 ,umol I-' glibenclamide had no effect on the resting potential, the overshoot, the half-depolarization time or the maximum rate of depolarization of action potentials, while the mean half-repolarization time increased by 19 ± 4 % (± S.E.M.) and the maximum rate of repolarization decreased by 17 + 5 %. 3. Fatigue was elicited using 100 ms tetanic contractions every I s for 3 min. In the absence of glibenclamide the mean half-repolarization time increased from 057 + 005 to 089 + 0 05 ms during fatigue. The mean half-repolarization times after fatigue, when muscle fibres were exposed to 100 ,umol I1 glibenclamide either 60 min prior to fatigue or 60 s before the end of fatigue, were 1-16 + 0-08 and 1t17 + 0 07 ms respectively.Application of 100 #smol I-' glibenclamide after 5 min of recovery did not increase the half-repolarization time, but decreased the rate of recovery compared to control values.4. In unfatigued muscles, 100 jumol I' glibenclamide did not affect the tetanic contraction. In the absence of glibenclamide, the mean tetanic force after fatigue was 11 0 + 0 9 % of prefatigue values. Application of 100 umol I' glibenclamide 60 min before fatigue increased the rate of fatigue development as the mean tetanic force was 4-8 + 0-8 % after 3 min of stimulation. The addition of 100 ,umol I-' glibenclamide 60 s before the end of fatigue had no effect on tetanic force during this time compared to control. 5. In the absence of glibenclamide, muscles recovered 90-1 + 1-6 % of their tetanic force after 100 min. Addition of 100,umol I' glibenclamide 60 min prior to fatigue significantly reduced the capacity of muscles to recover their tetanic force: after 100 min of recovery tetanic force was only 47-3 + 9.4 % of the pre-fatigue value. Application of 100 jumol I' glibenclamide 60 s prior to the end of fatigue had a much smaller effect on the recovery as 79.4 + 6'2 % of the tetanic force was recovered in 100 min. Addition of glibenclamide after 5 min of recovery had no effect. 6. The results from this study support the proposal that KATP channels are activated during fatigue and they contribute to the repolarization phase of the action potential. Although no evidence was found that activation of KATP channels during fatigue contributes to the force decrease during fatigue development, the impairment of force recovery following fatigue in the presence of glibenclamide supports the notion that KATP channels play an important protective role.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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The effect of glibenclamide on frog skeletal muscle: evidence for K+ATP channel activation during fatigue.

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Comtois

Renaud

1994

The Journal of Physiology

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“…Higher levels of SUR2 expression than SUR1 in skeletal muscle (167, 168), together with observations that cromakalim and pinacidil (SUR2-selective openers) (4, 331), typically stimulate skeletal muscle K ATP channels better than diazoxide (SUR1- or SUR2B-selective opener) (28, 35, 424) have led to the general assumption that skeletal muscle K ATP channels are formed of Kir6.2 plus SUR2A subunits. The conclusion is further supported by loss of K ATP activity in skeletal muscles from Kir6.2 −/− (274) and SUR2 −/− (55) animals.…”

Section: Katp In Skeletal Musclementioning

confidence: 99%

Muscle K_ATPChannels: Recent Insights to Energy Sensing and Myoprotection

Flagg

Enkvetchakul

Koster

et al. 2010

Physiological Reviews

251

272

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ATP-sensitive (KATP) channels are present in the surface and internal membranes of cardiac, skeletal and smooth muscle cell, and provide a unique feedback between muscle cell metabolism and electrical activity. In so doing, they can play an important role in the control of contractility, particularly when cellular energetics are compromised, protecting the tissue against calcium overload and fiber damage, but the cost of this protection may be enhanced arrhythmic activity. Generated as complexes of Kir6.1 or Kir6.2 pore-forming subunits with regulatory sulfonylurea receptor subunits, SUR1 or SUR2, the differential assembly of KATP channels in different tissues gives rise to tissue-specific physiological and pharmacological regulation, and hence to the tissue-specific pharmacological control of contractility. The last ten years have provided insights to the regulation and role of muscle KATP channels, in large part driven by studies of mice in which the protein determinants of channel activity have been deleted or modified. As yet, few human diseases have been correlated with altered muscle KATP activity, but genetically modified animals give important insights to likely pathological roles of aberrant channel activity in different muscle types.

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“…A class of pharmacological agents known as K+ channel openers has been shown to restore the membrane potential in diseased human skeletal muscle (Spuler, Lehmann-Horn & Grafe, 1989) and denervated mouse muscle (Hong & Chang, 1992), reduce the amplitude of the twitch in frog muscle (Sauviat, Ecault, Faivre & Findlay, 1991), and enhance Rb+ efflux from frog skeletal muscle (Benton & Haylett, 1992). The finding in these different studies, that this evoked K+ permeability was inhibited by sulphonylureas, led to the conclusion that the underlying mechanism responsible was probably activation of KATP channels.…”

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confidence: 99%

Activation of ATP‐dependent K+ channels by metabolic poisoning in adult mouse skeletal muscle: role of intracellular Mg(2+) and pH.

Allard

Lazdunski

Rougier

1995

The Journal of Physiology

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1. The effects of metabolic poisoning, intracellular Mg2+ and pH on ATP-dependent K+ (K+ATP) channels were examined in adult mouse isolated skeletal muscle fibres using the patch clamp technique. 2. In cell-attached membrane patches, while openings of one kind of channel could only rarely be detected under control conditions, cell poisoning with fluorodinitrobenzene (FDNB), dinitrophenol (DNP) and cyanide (CN) induced a strong and partially reversible increase in channel activity. 3. Slope conductance and glibenclamide sensitivity of this outward current indicated that the channel activated during poisoning was the KATP channel.4. Single channel current amplitude was reduced during poisoning, but remained unchanged when activation of the K+TP channel was induced by cromakalim. 5. In inside-out membrane patches, in the absence of intracellular ATP, intracellular application of Mg2+ decreased channel activity and single channel current amplitude. Inhibition of KATP channels by ATP was also reduced. 6. In the absence of intracellular ATP, a decrease in intracellular pH induced a reduction in channel activity and single channel current amplitude. Inhibition of KATP channels by ATP was also reduced. 7. The reduction of single channel current amplitude during poisoning was attributed to an increase in intracellular Mg2+ concentration caused by a fall in intracellular ATP concentration. These results also show that metabolic poisoning causes direct activation of K+TP channels in skeletal muscle, and that this activation is at least partially mediated through an increase in intracellular Mg2+ concentration and a decrease in intracellular pH.

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Effects of cromakalim on the membrane potassium permeability of frog skeletal muscle in vitro

Cited by 10 publications

References 25 publications

The effect of glibenclamide on frog skeletal muscle: evidence for K+ATP channel activation during fatigue.

The effect of glibenclamide on frog skeletal muscle: evidence for K+ATP channel activation during fatigue.

Muscle K_ATPChannels: Recent Insights to Energy Sensing and Myoprotection

Activation of ATP‐dependent K+ channels by metabolic poisoning in adult mouse skeletal muscle: role of intracellular Mg(2+) and pH.

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Effects of cromakalim on the membrane potassium permeability of frog skeletal muscle in vitro

Cited by 10 publications

References 25 publications

The effect of glibenclamide on frog skeletal muscle: evidence for K+ATP channel activation during fatigue.

The effect of glibenclamide on frog skeletal muscle: evidence for K+ATP channel activation during fatigue.

Muscle KATPChannels: Recent Insights to Energy Sensing and Myoprotection

Activation of ATP‐dependent K+ channels by metabolic poisoning in adult mouse skeletal muscle: role of intracellular Mg(2+) and pH.

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Muscle K_ATPChannels: Recent Insights to Energy Sensing and Myoprotection