Alteration of developing and adult rat muscle membranes by zuclomiphene and other hypocholesterolemic agents.

The present study presents evidence for a third hypocholesterolemic drug, zuclomiphene, being able to induce an experimental myotonic condition. Other drugs used singly or in combination were AY-9944, Triparanol and 20, 25-diazacholesterol. It has also been demonstrated for the first time that experimental myotonia can be induced in developing rats as well as adults. Developing rats received the initial intraperitoneal injections of drug at 5 days of age and were examined at 50 days of age. Adult rats were treated for 5 weeks. Two injections were given per week. Positive electromyography findings were observed in the developing and adult animals receiving 20, 25-diazacholesterol and zuclomiphene. The electromyography data of the other regimens of treatment were equivocal with regard to myotonia. Histological, histochemical, and electron microscopic examination of the muscle demonstrated no important changes. estimation of sterol composition showed that desmosterol was a major sterol in muscle after 20, 25-diazacholesterol or zuclomiphene treatment, thus furthering the concept that it is desmosterol in the muscle membrane, and not the drug, that is responsible for the myotonic condition.