Premium
The action of amyotrophic lateral sclerosis immunoglobulins on mammalian single skeletal muscle Ca2+ channels.
Author(s) -
Magnelli V,
Sawada T,
Delbono O,
Smith R G,
Appel S H,
Stefani E
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019504
Subject(s) - chemistry , nifedipine , calcium channel , agonist , dihydropyridine , medicine , endocrinology , voltage dependent calcium channel , electrophysiology , biophysics , calcium , receptor , biochemistry , biology , organic chemistry
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 microM), while it was decreased by the DHP antagonist nifedipine (5 microM). 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.