ANGIOTENSIN-II AND ANGIOTENSIN-CONVERTING ENZYME AS CANDIDATE COMPOUNDS MODULATING THE EFFECTS OF TESTIS ECDYSIOTROPIN IN TESTES OF THE GYPSY-MOTH, LYMANTRIA-DISPAR

Lymantria dispar testes synthesize immunodetectable ecdysteroid ill vi tro in response to the brain peptide, testis ecdysiotropin (TE), actin g primarily via a cascade involving G(i) protein, diacyl glycerol, and phosphokinase C. However, a component of TE activation also involves the opposite cascade, G(s) protein, cAMP, and phosphokinase A. Excess cAMP inhibits the action of TE, acting as a feedback modulator. Here, we show that bovine angiotensin II (AII) and bovine angiotensin conver ting enzyme (ACE) act like cAMP, inducing synthesis of immunodetectabl e ecdysteroid by pupal testes in vitro, but are antagonistic to coincu bated TE. In addition, an insect ACE antibody clearly stains the sperm atogenic cells through all stages of development, as well as testis sh eath tissue where ecdysteroid is synthesized. AII induces synthesis of cAMP by pupal testes ill vitro. Therefore, insect homologs of mammali an AII and ACE are good candidates for the peptides responsible for th e cAMP cascade and as modulators of TE action in lepidopteran testes. Saralasin, an analog of AII that blocks angiotensin receptors in mamma ls, behaved like AII in inducing ecdysteroid secretion with ecdysteroi dogenic effects additive to either angiotensin or ACE. Therefore, the receptors for the insect form of angiotensin on lepidopteran testis ce lls are probably different from those in mammals. Saralasin also inhib ited ecdysteroid synthesis when combined with TE, as did AII. (C) 1998 Academic Press.