Volume 21, Issue 3 pp. 329-335

Myasthenia gravis sera containing antiryanodine receptor antibodies inhibit binding of [3H]-ryanodine to sacroplasmic reticulum

Geir Olve Skeie MD

Corresponding Author

Geir Olve Skeie MD

Department of Neurology, University of Bergen, Bergen, Norway

Department of Neurology, University of Bergen, Bergen, NorwaySearch for more papers by this author
Per Kristian Lunde PhD

Per Kristian Lunde PhD

Institute for Experimental Medical Research, University of Oslo, Oslo, Norway

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Ole M. Sejersted MD

Ole M. Sejersted MD

Institute for Experimental Medical Research, University of Oslo, Oslo, Norway

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Åse Mygland MD

Åse Mygland MD

Department of Neurology, Vest-Agder Central Hospital, Kristiansand, Norway

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Johan A. Aarli MD

Johan A. Aarli MD

Department of Neurology, University of Bergen, Bergen, Norway

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Nils Erik Gilhus MD

Nils Erik Gilhus MD

Department of Neurology, University of Bergen, Bergen, Norway

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Abstract

Myasthenia gravis (MG) patients with thymoma often have antibodies against the calcium-release channel of the sarcoplasmic reticulum (SR) in striated muscle, the ryanodine receptor (RyR). RyR function can be tested in vitro by measuring the degree of [3H]-ryanodine binding to SR. In this study, sera from 9 out of 14 MG patients containing RyR antibodies inhibited [3H]-ryanodine binding to SR membranes from rat skeletal muscle. The 9 patients with antibodies inhibiting ryanodine binding had more severe MG than those with noninhibiting antibodies (P = 0.006). Sera from MG patients with acetylcholine receptor and titin muscle antibodies but no antibodies against RyR and blood-donor sera did not have an inhibiting effect in the [3H]-ryanodine binding assay. The results show that RyR antibodies in MG patients have high affinity for the RyR, and that the binding of antibodies probably affects calcium release from SR by locking the RyR ion channel in a closed position. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:329–335.

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