2ND MESSENGERS MEDIATING THE EFFECTS OF TESTIS ECDYSIOTROPIN IN TESTES OF THE GYPSY-MOTH, LYMANTRIA-DISPAR

Exposure of larval and pupal testes of Lymantria dispar to diacyl glyc erol mimics, phorbol, 12-myristate, 13-acetate, and 11, 12 dibutyryl p horbol ester, induced or augmented synthesis of immunodetectable ecdys teroids. The non-esterified analog, 4alpha-phorbol, had little effect. H-7, a protein kinase C inhibitor, inhibited ecdysteroid synthesis. W hen testis ecdysiotropin and phorbol esters were administered together at the maximum effective dose of each, steroidogenesis was further en hanced. Therefore, diacyl glycerol may be a second messenger for testi s ecdysiotropin in testes. In addition, testis ecdysiotropin induced a rapid rise and fall in cAMP titers in both larval and pupal testes. T he cyclic AMP analog, dibutyryl cyclic AMP, induced ecdysteroid synthe sis in larval testes, but had little steroidogenic effect in pupal tes tis sheaths. However, dibutyryl cyclic AMP inhibited the steroidogenic effect of testis ecdysiotropin in larval as well as pupal testes. Cyc lic AMP may act to modulate the effects of testis ecdysiotropin in ind ucing ecdysteroid synthesis by testes of L. dispar.