TRANSDUCTION OF THE SIGNAL INITIATED BY THE NEUROPEPTIDE, TESTIS ECDYSIOTROPIN, IN TESTES OF THE GYPSY-MOTH, LYMANTRIA-DISPAR

Testes of Lymantria dispar synthesize immunologically detectable ecdys teroid in vitro. Early last instar larval testes can be induced to pro duce ecdysteroid de novo by means of the brain peptide, testis ecdysio tropin (TE), although testes excised in mid pupal stage synthesize ecd ysteroid without TE stimulus in vitro; they can be boosted to higher l evels of synthesis with TE. By use of agents H-7 and H-8, inhibitors o f phosphokinases C (PKC) and cAMP-dependent protein kinase (PKA), resp ectively, we have confirmed previous data indicating that diacyl glyce rol and its effector, PKC, are second messengers for the TE message. I n larval testes, but not pupal testes, cAMP and PKA also regulate ecdy steroid synthesis. Data obtained from incubation of testes with analog s of GTP (GTP gamma S) and GDP (GDP beta S) and the ribosylating agent s, pertussis and cholera toxins, indicate that TE is transduced via in hibiting G protein (G(i)) in larval testes, although both G(i) and sti mulating G protein (G(s)) influence ecdysteroid synthesis in pupal tes tes. Synthesis must be further modulated by feedback loops operating w ith G(s) and G(i) controlled factors in testes exposed to TE. Ecdyster oid synthesis appears to be constitutive in pupal testes in the absenc e of exogenous TE.