The herbicides amiprophosmethyl (APM) trifluralin, and oryzalin as well as the fungicides methylbenzimidazolyl carbamate (MBC), O-isopropyl N-phenyl carbamate (IPC), and chlorisopropyl N-phenyl carbamate (CIPC), which are known to cause the destruction of microtubules in vivo but do not interfere with tubulin polymerization in vitro, have been examined with respect to their ability to affect Ca2+transport in isolated cell organelles. In contrast to colchicine which has no effect on Ca2+transport in isolated mitochondrial and microsomal fractions, all of the substances investigated caused considerable reduction of ca2+net uptake into mitochondrial but not into microsomal fractions. This reduction has been shown to be due to an increase in passive Ca2+efflux. These results have been extrapolated to in vivo situations where they are postulated to act by raising cytoplasmic Ca2+levels.
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