Studies on the mode of action of ecdysterone in adult female Aedes aegypti.

Injection of ecdysterone into non-blood fed adult female Aedes aegypti results in a marked stimulation of aromatic-L-amino-acid decarboxylase (formerly DOPA-decarboxylase) activity (Schlaeger and Fuchs, 1974a). When the hormone and alpha-amanitin are injected either simultaneously or if the toxin is administered first no inhibition of subsequent enzymatic activity is observed and in fact substantial enhancement occurs. Cordycepin injection along with ecdysterone gives results similar to alpha-amanitin. The inhibitors by themselves elicit a very small increase in DOPA decarboxylase activity compared to saline-injected controls. Conversely, actinomycin D causes severe depression of ecdysterone-mediated DOPA decarboxylase activity as dose cycloheximide and puromycin. We interpret our data to mean that the mRNA for DOPA decarboxylase is already present prior to exposure to ecdysterone. We postulate that the function of the hormone would be to modulate translation of specific pre-formed mRNA's by an unknown mechanism or to induce transcription of specific tRNAs necessary for the initation of translation of selecting existing messengers.