[The cyclic nucleotide system of Aspergillus nidulans under the influence of methylbenzimidazol-2-ylcarbamate (MBC). I. A hypothetical mitosis model].

The influence of methylbenzimidazol-2-yl carbamate (MBC) on the cyclic nucleotide system of germinating Aspergillus nidulans conidia has been investigated throughout the cell cycle. The content in cyclic adenosine 3',5'-monophosphate (cAMP) and cyclic guanosine 3',5'-monophosphate (cGMP) is rapidly decreased in the course of conidia swelling and has been found not to be influenced by MBC. On the other hand, influence of MBC leads, in inhibited nuclear division, to a significant increase of the intracellular cAMP level in the G2-period between the eighth and tenth hour after incubation. The adenylate cyclase activity has not been significantly influenced during this period by MBC treatment. On the contrary, the cAMP-specific phosphodiesterase activity has been decreased. The cGMP content of germinating conidia decreased, contrary to cAMP by MBC treatment between the seventh and twelfth hour. Activity of guanylate cyclase has been generally stimulated in the presence of MBC, whereas that of the cGMP-specific phosphodiesterase as a result of mitosis inhibition has been blocked. the influence of the cyclic nucleotide system on mitosis is discussed in terms of a hypothetical model.