Abstract
Myotonia induced in rats by 20,25-diazacholesterol is accompanied by accumulation of desmosterol in serum, fragmented sarcoplasmic reticulum, and sarcolemma. Activities of (Na + ,K + )- and Ca 2+ -stimulated adenosine triphosphatases of the sarcolemma are increased, but not the Mg 2+ -stimulated adenosine triphosphatase. The altered sterol composition of the sarcolemma may cause this type of myotonia by decreasing the chloride conductance of the membrane.