Allatostatic regulation of juvenile hormone production in vitro by the ring gland of Drosophila melanogaster

Abstract

A factor(s) extracted from the third instar larval brains of the dipteran species Sarcophaga bullata and Drosophila melanogaster causes a dose-dependent reduction of juvenile hormone (JHB 3) biosynthesis by isolated ring glands in vitro. In situ, this factor is presumably neuronally transmitted from the brain to ring gland. The allatostatic effect of the brain factor is reversible in vitro and may be overcome partially by the JHB 3 precursor farnesoic acid. Agents which act to increase the intracellular levels of cAMP (3-isobutyl-1-methylxanthine (MIX), forskolin, 8-benzoyl cAMP) all caused the reduction of JHB 3 synthesis in vitro in a reversible manner. The inhibitory effect of increased levels of cAMP was overcome by the addition of farnesoic acid to the culture medium. The dependence of JHB3 synthesis on extracellular calcium was demonstrated by incubation of ring glands in the presence of the Ca 2+ channel blocker lanthanum chloride, and in Ca 2+-free medium containing EGTA. The inclusion of farnesoic acid abolished the zero Ca 2+ effect completely. However, the Ca 2+ ionophore A23187 inhibited JHB 3 production in medium containing Ca 2+ suggesting that elevated intracellular levels of Ca 2+ also suppress JHB 3 production. This latter inhibition could not be reversed completely by farnesoic acid.