Similarity of ATP‐dependent K+ channels in skeletal muscle fibres from normal and mutant mdx mice.

Abstract

1. ATP-dependent K+ (KATP) channels were studied in fibres isolated from flexor digitorum brevis and interosseal skeletal muscles of normal and mutant mdx mice using the patch clamp technique in the presence of asymmetrical K+ concentrations (5 mm K+ in the pipette and in vivo intracellular [K+] or 145 mm K+ at the cytoplasmic face). 2. In cell-attached patches from mdx muscle fibres bathed in K+-rich solution, cell poisoning with fluorodinitrobenzene induced partially reversible opening of channels carrying an outward current of an amplitude of 1P2 pA at 0 mV. Exposure of fibres to the K+ channel opener cromakalim led to opening of the same type of channel. These channels were assumed to be KATP channels. 3. On excision of inside-out patches from mdx muscle fibres, in the absence of intracellular ATP, KATP channels were active: they carried a unitary outward current of 1 6 pA at 0 mV and were inhibited by intracellular ATP and glibenclamide. The number of KATP channels per patch was not significantly different in muscles from normal and mdx mice.4. In inside-out patches, in the presence of 1 mm intracellular Mg2+, slope conductances of 21 and 203 pS were found for KATP channels in normal and mdx muscle, respectively. In the absence of Mg2+, slope conductances of KATP channels were 31-3 and 32 pS in normal and mdx muscle, respectively and KATP channel activity was' augmented in mdx muscle in the same way as in normal muscle. Activity of the same KATP channel was observed in extensor digitorum longus muscle from normal and mdx mice. 5. In inside-out patches held at 0 mV, the relationship between KATP channel activity and intracellular ATP was described by a Hill equation: K1 values were 23 and 21 /SM and Hill coefficients were 1 8 and 1'9 in normal and mdx muscle, respectively. 6. These results indicate that the distribution, the conductance properties and ATP sensitivity of KATP channels do not differ in normal and in mdx mouse skeletal muscle.

Elevated subsarcolemmal Ca 2+ in mdx mouse skeletal muscle fibers detected with Ca 2+ -activated K + channels

“…In these experiments, membrane patches were clamped at 0 mV and exposed in a cumulative manner to internal solutions containing increasing concentrations of free Ca 2ϩ . In the presence of 1.7 M calcium at the cytoplasmic face, opening of channels that correspond to ATP-dependent K ϩ channels, as described in a previous study with similar experimental conditions (28,29), were detected both in control and mdx muscle fibers. At 3 M Ca ] in control and mdx muscle fibers.…”

Maturation and myotonia influence the abundance of cation channels KDR, KIR and CIR differently: a patch-clamp study on mouse interosseus muscle fibres

“…This is in contrast to recordings from membrane patches excised from skeletal muscle fibres [1,39]. Our results are in accordance with the finding that K Ca does not play a major role for resting G K in muscle fibres of adult (but not aged) rats [35].…”

Ion Channels of the Sarcolemma and Intracellular Organelles in Duchenne Muscular Dystrophy: A Role in the Dysregulation of Ion Homeostasis and a Possible Target for Therapy

“…The decrease in K ATP channel activity is known to be closely associated with the development of various forms of cardiomyopathy [95,96] and, apparently, also contributes to the development of cardiac pathology characteristic of the late stages of DMD. At the same time, in the case of skeletal muscles, it is noted that distribution, the conductance properties, and ATP sensitivity of K ATP channels do not differ in wild-type and in mdx animals [97].…”