Captopril, a specific inhibitor of angiotensin converting enzyme, enhancesboth trypsin and vitellogenin titers in the grey fleshfly Neobellieria bullata

A strong and constitutive angiotensin converting enzyme- or ACE-like activi ty was demonstrated in the hemolymph of the adult grey fleshfly Neobellieri a bullata, In a competition assay, the N. bullata trypsin modulating oostat ic factor (Neb-TMOF) was confirmed to be an in vitro substrate for this cir culating Neb-ACE, Oral uptake of captopril, a selective and specific inhibi tor of ACE, resulted in a complete phenotypic knockout of circulating ACE a ctivity. When compared with control animals, captopril-fed female flies sho wed an increase in the liver meal-induced trypsin peak in the midgut and el evated levels of protein meal-induced yolk polypeptides in the hemolymph, T he latter effect was not due to a slower vitellogenin uptake by the ovaries , because oocyte growth was not affected by the captopril treatment. The ap parent synergism between the demonstrated ACE functionality and the previou sly reported effects of the oostatic peptide Neb-TMOF are discussed in the context of our recent finding that Neb-TMOF represents a prime candidate fo r being the first known in vivo substrate for circulating insect ACE. (C) 2 001 Wiley-Liss, Inc.