Desmosterol accumulation in rats with experimental myotonia.

Desmosterol is found in various organs of rats that show signs of myotonia in their skeletal muscle as a result of treatment with 20.25diazacholesterol. The amount of desmosterol depends on the time of treatment, and is different in different organs and different kinds of muscle. The increase in desmosterol is much lower and the rats do not show any signs of myotonia when fed a cholesterol rich diet in addition to treatment with 20.25-diazacholesterol. Treatment with triparanol also causes desmosterol accumulation but in these rats myotonia is rarely observed. Our results suggest that in the experimental animals myotonia becomes manifest when every second cholesterol molecule of the muscle cell membrane is replaced by desmosterol. This is easily achieved in animals fed with 20.25-diazacholesterol but rarely occurs with triparanol.