Injection of Dip-allatostatin or Dip-allatostatin pseudopeptides into mated female Diploptera punctata inhibits endogenous rates of JH biosynthesis and basal oocyte growth

Studies on the catabolism of allatostatins (ASTs) provided the rationale fo r the design of a series of Dip-allatostatin-derived pseudopeptide mimetic analogues. In vitro, the Dip-ASTs and pseudopeptides show varying degrees o f resistance to catabolism and all show significant inhibition of juvenile hormone (JH) biosynthesis. This study was undertaken to determine whether p otent Dip-ASTs and/or their pseudopeptide mimetic counterparts caused 'alla tostatic' effects in vivo following injection into mated female Diploptera punctata. Animals injected with aqueous solvent or Dip-AST 7(1-7) N-termina l fragment, which excludes the active core region of the ASTs, were used as controls. An in vitro radiochemical assay revealed that injection of Dip-A ST 5, 7 or pseudopeptide analogues 397-2 or AST(b)phi 2 significantly inhib ited the biosynthesis of JH (P<0.05). The results also indicate that basal oocyte growth was significantly inhibited by injection of these same compou nds, with the exception of Dip-AST 7 (P<0.05). Analogues 396-1 and 419 did not significantly inhibit rates of JH biosynthesis but did significantly in hibit the growth of basal oocytes. Analyses of feeding, excretion and food absorption/utilization patterns of these same animals suggested that these compounds are not toxic to the insect; rather they directly inhibit the bio synthesis of JH by the corpora allata, and reduce the rate of growth of bas al oocytes. Disruption of critical reproductive and/or developmental proces ses by pseudopeptide analogues of the ASTs could provide novel and selectiv e strategies for future insect pest management. (C) 2000 Elsevier Science L td. All rights reserved.