A series of Vinca alkaloids were found to block polymerization of crude tubulin extracts of porcine brain in a dose-dependent manner. This appears to be a specific effect occurring at low concentrations of drug. The concentration of vinblastine that prevents polymerization by 50% was 4.3 × 10-7 mole/liter for a tubulin concentration of 3.0 mg/ml, and this concentration is consistent with levels achieved in vivo following routine pharmacological doses in humans.


This work was supported by NIH Grant CA 06973 and by the Eli Lilly Company.

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