Acetylcholine receptors and myasthenia gravis: the effect of antibodies to eel acetylcholine receptors on eel electric organ cells.
Antisera to acetylcholine receptors purified from Electrophorus electricus were tested for their ability to bind to receptors on electric organ cells, block the depolarizing response of the cells to carbamylcholine, and inhibit binding of 125-I-alpha-bungarotoxin to the cells. It was found that although antibodies could bind to most of the receptors, resulting in substantial inhibition of the depolarizing response, binding of 125-I-alpha-bungarotoxin to the cells was only slightly inhibited. This was consistent with the observation that these antibodies did not compete for the toxin binding site on detergent-solubilized receptor. These results suggest that the antibodies inhibited receptor activity primarily by interfering with the ionophore of the receptor or its regulation by the acetylcholine binding site. However, the possibilities could not be completely eliminated that blockage of a small fraction of the binding sites caused a large inhibition of the depolarizing response or that bound antibody allosterically reduced binding affinity for carbamylcholine without completely inhibiting toxin binding.
D000818:Animals; D000906:Antibodies; D002217:Carbachol / Q000494:pharmacology; D004306:Dose-Response Relationship, Immunologic; D004557:Electric Organ / Q000187:drug effects / Q000276:immunology*; D004586:Electrophoresis; D005071:Evoked Potentials; D009157:Myasthenia Gravis / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000276:immunology*
D000906:Antibodies; D011950:Receptors, Cholinergic; D002217:Carbachol