Calcium increase in mouse skeletal muscles by triparanol: a drug to induce myotonic dystrophy-like clinical manifestations.

Triparanol (Trp) is known to cause clinical features similar to those seen in myotonic dystrophy, including myotonia, cataract and baldness. To explore the pathophysiological mechanism of myotonic dystrophy, we examined the effect of Trp on intracellular calcium in cultured skeletal myoblasts and myotubes as well as cardiac myocytes by using a fluorescent indicator. Trp preferentially induced increase of intracellular calcium in myotubes of skeletal muscles. Since the increase of calcium was inhibited by thapsigargin pretreatment but not by extracellular calcium elimination, it appears that triparanol might act mostly on intracellular calcium stores. Trp also inhibited the increase of calcium in myotubes induced by acetylcholine. Trp might cause myotonia possibly through the increase of intracellular calcium from intracellular stores.