Mg2+ dependence of Ca2+ release from the sarcoplasmic reticulum induced by sevoflurane or halothane in skeletal muscle from humans susceptible to malignant hyperthermia  A.M. Duke, P.M. Hopkins, P.J. Halsall, D.S. Steele  British Journal of Anaesthesia  Volume 97, Issue 3, Pages 320-328 (September 2006) DOI: 10.1093/bja/ael179 Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 1 Effects of sevoflurane or halothane in MHN fibres. (a) Recordings of the fura-2 fluorescence ratio from two mechanically skinned MHN fibres. The preparations were perfused with solutions containing 120 nM Ca2+ and 1 mM [Mg2+]. A series of Ca2+ transients (two shown) was induced by brief application of 40 mM caffeine/zero Mg2+ at 4 min intervals. After a further 4 min Ca2+ loading period, 5 mM halothane (upper) or 5 mM sevoflurane (lower) was introduced rapidly and perfusion stopped. This protocol was then repeated with 10, 20 or 40 mM halothane or sevoflurane present during the period of zero perfusion. After exposure to halothane or sevoflurane, perfusion was restarted and 40 mM caffeine was reapplied at 4 min intervals to assess possible deterioration (one response shown). (b) Accumulated data showing the percentage of responsive fibres at each concentration of halothane or sevoflurane (n=20, one fibre per patient). British Journal of Anaesthesia 2006 97, 320-328DOI: (10.1093/bja/ael179) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 2 [Mg2+] dependence of halothane or sevoflurane-induced Ca2+ release in MHN fibres. (a) Fluorescence ratio records showing changes in [Ca2+] within a mechanically skinned MHN muscle fibre. The preparation was initially perfused with a solution containing 120 nM Ca2+ and 1 mM [Mg2+]. A series of Ca2+ transients (two shown) was induced by brief application of 40 mM caffeine/zero Mg2+ at 4 min intervals. After a further 4 min Ca2+ loading period in the presence of 1 mM Mg2+, perfusion was stopped and the solution replaced with an identical solution (not shown). One minute later, the solution was exchanged rapidly for one containing 1 mM Mg2+/1 mM halothane and the flow again stopped. This protocol was repeated in the same preparation, but with 0.4 mM Mg2+ present during the initial stop-flow period and subsequent exposure to halothane. (b) Results obtained on the same MHN fibre with 1 mM sevoflurane replacing halothane in the sequence. British Journal of Anaesthesia 2006 97, 320-328DOI: (10.1093/bja/ael179) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 3 [Mg2+] dependence of halothane or sevoflurane-induced Ca2+ release in MHS fibres. (a) Fluorescence ratio records showing changes in [Ca2+] within a mechanically skinned MHS fibre. The preparation was initially perfused with a solution containing 120 nM [Ca2+] and 1 mM [Mg2+]. A series of Ca2+ transients (two shown) was induced by brief application of 40 mM caffeine/zero Mg2+ at 4 min intervals. After a further 4 min Ca2+ loading period in the presence of 1 mM Mg2+, perfusion was stopped and the solution replaced with an identical solution (not shown). One minute later, the solution was exchanged rapidly for one containing 1 mM Mg2+/1 mM halothane and the flow again stopped. This protocol was repeated in the same preparation, but with 0.4 mM Mg2+ present during the initial stop-flow period and subsequent exposure to halothane. (b) Results obtained on the same MHS fibre with 1 mM sevoflurane replacing halothane in the sequence. British Journal of Anaesthesia 2006 97, 320-328DOI: (10.1093/bja/ael179) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 4 [Mg2+] dependence of halothane or sevoflurane-induced Ca2+ release: accumulated data. Accumulated data showing the percentage of fibres responding to 1 mM halothane or 1 mM sevoflurane as a function of [Mg2+] in MHS (a) or MHN (b) fibres. All data were obtained using the protocol shown in Figures 2 and 3. Values are expressed as a percentage of the total number of fibres: MHN, 33; MHS, 13 (one fibre per patient). British Journal of Anaesthesia 2006 97, 320-328DOI: (10.1093/bja/ael179) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions