Systemic effects of podophyllotoxin on phosphate metabolism in innervated and denervated, slow and fast muscles of the rat.

The systemic administration of podophyllotoxin gives qualitatively the same results as the administration of colchicine. It increases the specific activities and isotope uptakes of the inorganic phosphate and acid-soluble organic-bound phosphate fractions of slow and fast muscles. In the extensor digitorum longus muscles these increases are slowly reversible. In the two fast muscles -- gastrocnemius and extensor digitorum longus muscles -- significant interactions between podophyllotoxin treatment and 3 d-surgical denervation are observed. It is proposed that, like colchicine, podophyllotoxin induces denervation-like alterations in the Pi and POAS metabolism of skeletal muscle. In view of their structural dissimilarities it is further proposed that their action on muscle phosphate metabolism is mediated through a common property : i.e. binding to muscle free tubulin.