An ultrastructural examination of the action of vinblastine on microtubules, neurofilaments and muscle filaments in vitro.

In vitro incubation of autonomic nerves with vinblastine sulphate (1 times 10(-4) M) caused a disappearance of microtubules within 15 min; during the following 15 min paracrystalline arrays appeared within the axons. An increase in the abundance of microfilaments was also observed, but these did not appear to arise from disaggregated microtubules since the increase in microfilament numbers was noted at an incubation time when crystal formation was extensive. Pretreatment of autonomic nerves with colchicine (2.5 times 10(-4) M) caused a reduction of approximately 80% in the numbers of microtubules, but did not prevent the formation of crystals on subsequent exposure to vinblastine. No ultrastru"tural changes were observed in myofilaments on incubation with vinblastine.