A Simple Method for Determining Antitubulinic Activities of Ansamitocins and Related Compounds Using a Cilia Regeneration System with Deciliated Tetrahymena

Cilia regeneration with deciliated Tetrahymena pyriformis W was tested to determine the antitubulinic activities of ansamitocins and related compounds in a microbial system. Various factors interfered with the regeneration process, i.e. excess shearing force in deciliation procedure, high temperature (32°C or above), high or low pH (pH 9 or 5), and exogenous divalent cations, such as Zn²⁺, Mn²⁺, Cu²⁺ and Co²⁺. Under suitable conditions, cilia regeneration was completed in about 60 min of incubation, and a number of newly formed cilia were observed around the cell surface. When ansamitocins were added to the recovery solution, cilia regeneration was completely suppressed without alterations in cell shape or the surface structure of deciliated Tetrahymena. In this assay system, the inhibitory activity of ansamitocins was slightly stronger than that of maytansine.