Myasthenia gravis. I. Importance of potassium in inhibitory action of normal and myasthenic thymus extracts.

Abstract

SummaryA method is described which permits recording of the isolated myogram of indirectly or directly stimulated isolated frog saritorius muscle. 2. Acetone extracts prepared from thymus glands obtained from 16 myasthenic patients, one normal child's thymus, 3 spleens and 2 samples of striated muscle were tested on the isolated frog sartorius preparation. 3. Both acetone soluble and acetone insoluble fractions markedly decrease the muscle tension curve in 2 to 20 minutes. When the muscle becomes inexcitable on indirect stimulation, it is also inexcitable on direct stimulation. 4. The active material is heat stable, dialysable and is antagonized by CaCl2 added to the extracts. 5. Concentrations of potassium 2 to 44 times the potassium concentration of frog Ringer were found in the extracts. These concentrations of potassium are sufficient to produce the muscle inhibition observed. 6. The significance of these results relevant to the search for a blocking agent in the thymus glands of myasthenic patients i...