Effects of anti-microtubule agents on Paramecium cell culture growth

Since there are no systematic studies available on the effects of anti-microtubule agents on ciliated protozoa, we screened a wide variety of such compounds for their effects on the growth of Paramecium tetraurelia cell cultures. Compounds tested include agents of widely different chemical composition and with reported effects on widely different cell types. We can differentiate between different drug effects: (a) Rotenone is the only agent without any recognisable effect, (b) Another group of compounds (including colchicine) requires very high concentrations, as compared to higher animal cells, i.e., rather close to a cytotoxic level; this group also includes tubulozole (unexpectedly without any difference between the cis- and the trans-stereoisomer). (c) A third group of drugs inhibits cell culture growth without any lethal effects (benzimidazoles, nocodazole, parbendazole; the [anti-]fungal antibiotic, griseofulvin; the herbicide, trifluralin). (d) Finally a group of agents are active in a concentration range also reported for plants (the herbicide, APM) or for higher animal cells (including the microtubule stabiliser, taxol) or for both (vinblastine, vincristine, triethyl lead), although they are cytotoxic at higher concentrations (like compounds of group [b]). Therefore, in particular compounds of group (c) and possibly of group (d) might be considered further on for a more detailed analysis of a possibly genuine anti-microtubular effect in Paramecium cells. Of particular interest may be nocodazole, parbendazole and trifluralin, since they can inhibit cell culture growth (over 24 h tested) in relatively low concentrations (comparable to other cell types) without any impairment of cell viability.