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I Na and I Kir are reduced in Type 1 hypokalemic and thyrotoxic periodic paralysis
Author(s) -
Puwanant Araya,
Ruff Robert L.
Publication year - 2010
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21693
Subject(s) - hypokalemic periodic paralysis , chemistry , hypokalemia , periodic paralysis , repolarization , medicine , endocrinology , muscle fibre , euthyroid , membrane potential , electrophysiology , paralysis , skeletal muscle , thyroid , biochemistry , surgery , organic chemistry
We evaluated voltage‐gated Na + (I Na ) and inward rectifier K + (I Kir ) currents and Na + conductance (G Na ) in patients with Type 1 hypokalemic (HOPP) and thyrotoxic periodic paralysis (TPP). We studied intercostal muscle fibers from five subjects with HOPP and one with TPP. TPP was studied when the patient was thyrotoxic (T‐toxic) and euthyroid. We measured: (1) I Kir , (2) action potential thresholds, (3) I Na , (4) G Na , (5) intracellular [Ca 2+ ], and (6) histochemical fiber type. HOPP fibers had lower I Na , G Na , and I Kir and increased action potential thresholds. Paralytic attack frequency correlated with the action potential threshold, G Na and I Na , but not with I Kir . G Na , I Na , and [Ca 2+ ] varied with fiber type. HOPP fibers had increased [Ca 2+ ]. The subject with TPP had values for G Na , I Na , action potential threshold, I Kir , and [Ca 2+ ] that were similar to HOPP when T‐toxic and to controls when euthyroid. HOPP T‐toxic TPP fibers had altered G Na , I Na , and I Kir associated with elevation in [Ca 2+ ]. Muscle Nerve, 2010