The action of amyotrophic lateral sclerosis immunoglobulins on mammalian single skeletal muscle Ca2+ channels.

V. Magnelli, T. Sawada, O. Delbono, R. G. Smith, Stanley H. Appel, E. Stefani

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

1. The planar phospholipid bilayer technique was used to study the T-tubule skeletal muscle dihydropyridine (DHP)sensitive calcium (Ca2+) channel. To improve the signal-to-noise ratio, Ca2+ channel activity was recorded using both 800-50 and 500-50 mM NaCl gradients. 2. Ca2+ channels were characterized by their cation selectivity and pharmacological profile. The mean open time for channels identified by these techniques was increased by the DHP agonist Bay K 8644 (2 μM), while it was decreased by the DHP antagonist nifedipine (5 μM). Nifedipine also reduced Ca2+ channel amplitude levels. 3. Immunoglobulins G (IgG) from three amyotrophic lateral sclerosis (ALS) patients (n = 14 experiments), one myasthenia gravis (MG) patient (n = 3 experiments) and one healthy individual (n = 4 experiments), were tested on Ca2+ channel activity at a final concentration of 3 mg/ml. 4. Channel mean open time, mean closed time and time integral for the current were not modified by normal IgG (n = 4 experiments). Similarly, MG IgG did not reduce channel activity (n = 3 experiments). 5. ALS IgG reduced the mean open time of DHP-sensitive Ca2+ channel activity in twelve out of fourteen experiments. In addition, in five out of twelve experiments, ALS IgG stabilized the channel to a smaller amplitude level. 6. ALS IgG reduced Ca2+ channel activity in a side-selective fashion, probably corresponding to the external side of the channel. 7. These results suggest that ALS IgG action on DHP-sensitive Ca2+ channels is not mediated by second messengers, thus favouring a direct mechanism for interaction with the DHP receptor complex.

Original languageEnglish (US)
Pages (from-to)103-118
Number of pages16
JournalThe Journal of Physiology
Volume461
Issue number1
DOIs
StatePublished - Feb 1 1993

ASJC Scopus subject areas

  • Physiology

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