Effects of methylmercury and inorganic mercury on the growth of nerve fibers in cultured chick dorsal root ganglia

Inhibition of the growth of nerve fibers by mercurials was quantitatively e stimated by measuring the length of fibers in the cultured chick dorsal roo t ganglion, Morphological changes in nonneuronal cells were also evaluated. The growth rates of nerve fibers were constant for 2 to 6 days after the s tart of incubation. Methylmercury depressed nerve fiber growth dose- and ti me-dependently by 50% and completely at 3 x 10(-6) M and 7 x 10(-6) M, resp ectively. About 10-fold higher concentrations of inorganic mercury were req uired for the same extent of inhibition. The nerve fibers exposed to inorga nic mercury shrank at an early stage of exposure and thereafter grew again within 24 hours. Electron microscopic examination revealed that methylmercu ry decreased microtubule mass extensively in nerve fibers, while inorganic mercury markedly altered surface membrane structure. These results suggeste d that microtubule disruption is involved in methylmercury induced depressi on of nerve fibers but not in that induced by inorganic mercury. Characteri stic effects on the growth of nerve fibers and the proliferation of nonneur onal cells mere observed on the treatment with other metals such as cadmium , silver and chromium, Thus, dorsal root ganglion culture seems to be usefu l for the evaluation of toxic effects of metals in vitro.