Involvement of adenosine cyclic-3 ',5 '-monophosphate in the signal transduction pathway of mandibular organ-inhibiting hormone of the edible crab, Cancer pagurus

The juvenoid, methyl farnesoate (MF), is synthesized in the mandibular orga ns (MOs) of crustaceans, under the control of mandibular organ-inhibiting h ormone (MO-IH). Using an in vitro assay to measure synthesis of MF by MOs, the effect of a variety of agents that affect signal transduction pathways was investigated. Of the compounds tested, only agents which affect cAMP (f orskolin and 8-bromoadenosine cyclic-3',5'-monophosphate) levels were found to mimic the inhibitory action of MO-IH on MF synthesis. To further suppor t these findings, the effect of MO-IH-1 on production of cAMP was investiga ted. The results demonstrated that MO-III stimulated a dose-dependent incre ase in cAMP levels. Furthermore, a maximal 2-fold increase in cAMP was dete cted after a 5-min exposure of MO membranes to 100 nM MO-IH-1, falling to b asal levels thereafter. The results presented strongly support a role for c AMP in the signal transduction mechanism of MO-IH that leads to inhibition of MF synthesis in MOs. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.