Nocodazole, vinblastine, and taxol at low concentrations affect fibroblastlocomotion and saltatory movements of organelles

Microtubules (MTs) are essential for maintenance of asymmetric cell shape a nd motility of fibroblasts. MTs are considered to function as rails for org anelle transport to the leading edge. We investigated the relationship betw een the motility of Vero fibroblasts and saltatory movements of particles i n their lamella. Fibroblasts extended their leading adges into the experime ntal wound at a rate of 20 +/- 11 mu m/h. The intracellular particles in th e front parts of the polarised fibroblasts moved saltatory mainly along the long axis of the cells. MTs depolymerization induced by the nocodazole at a high concentration (1,7 mu M) resulted in the inhibition of both fibrobla st motility and saltatory movements of the particles. Taxol (1 mu M)inhibit ed fibroblasts movement but not the saltatory movements. The saltatory move ments pattern was disorganised by taxol by decreasing a portion of longitud inal saltations and consequently by increasing the part of saltations perpe ndicular to the cell long axis. This effect may be explained by disorganisa tion of the MTs network resulting from the inhibition of the dynamic instab ility. To further investigate the relationships between the MTs dynamis ins tability; saltatory movements, and fibroblasts locomotion, we treated fibro blasts with microtubule drugs at low concentration (nocodazole, 170 nM; vin blastine, 50 nM; and taxol, 50 nM). All these drugs induced rapid disorgani zation of the saltatory movements and decreased the rate of cell locomotion : Simultaneously, the amount of acetylated (stable) MTs increased. Also the treatment induced reversible changes in the actin meshwork. We suggest tha t decrease in the fibroblast locomotion rate in the case of MTs stabilizati on occured because df the appearance of numerous free MTs. Saltations along free MTs are poorly organized, and as a result of it, the number of organe lles reaching the fibroblast leading edge decrease.