ALLATOSTATIN CONTENT OF BRAIN, CORPORA ALLATA AND HEMOLYMPH AT DIFFERENT DEVELOPMENTAL STAGES OF THE COCKROACH, DIPLOPTERA-PUNCTATA - QUANTITATION BY ELISA AND BIOASSAY

The quantity of allatostatin-like peptide in brain, corpora allata, haemolymph and that released from corpora allata in vitro was determined for adult female Diploptera punctata. The quantity of allatostatin was also measured in haemolymph of last-instar females. A sensitive enzyme-linked immunosorbent assay (ELISA), utilizing an antibody specific for allatostatin 1, and an in vitro bioassay were used for this quantitation. Allatostatin 1 content of brain extract determined by ELISA showed changes which correlated with the reproductive cycle of mated females but no changes in virgin females. In vitro bioassay confirmed a lesser quantity of allatostatins in brain and in corpora allata of females during vitellogenesis and during pregnancy, relative to females immediately after vitellogenesis (maximum of 3.75 pmol/brain). The quantity of allatostatin 1-immunoreactive material in haemolymph of mated females also varied with the reproductive cycle: low during vitellogenesis, a sharp increase at oviposition to a maximum (2.25 nM) early in pregnancy (day 13) followed by a decline. In haemolymph of last instars, the concentration was low in the first half of the stadium but increased dramatically (1.27 nM) in the latter half of the stadium when juvenile hormone production is undetectable. Allatostatin was released from corpora allata in vitro at a high rate between 1.5 and 4 h and decreased thereafter. Treatment of corpora allata in vitro with high potassium ion also elicited an increase in allatostatin release, as determined both by ELISA and by bioassay. The presence of allatostatin-immunoreactive material in the haemolymph suggests a humoral pathway for the action of these compounds, in addition to a nervous pathway from the brain.