EFFECTS OF JUVENILE-HORMONE ON POLYAMINES OF THE FAT-BODY AND NEURAL TISSUE OF THE CRICKET ACHETA-DOMESTICUS

The levels of polyamines and the activity of two of the rate limiting enzymes of their biosynthesis were studied in neural tissue and in the fat body of adult females of Acheta domesticus, submitted to differen t physiological experiments. Allatectomy, performed during the last la rval instar, suppressed juvenile hormone production, resulted in the a bsence of the peak of hormone occurring in 3-day-old adult females and affected the normal pattern of polyamine distribution. As early as da y 4 post-emergence, putrescine titres markedly decreased in the fat bo dy, and spermidine levels dropped in the neural tissue. In the fat bod y, allatectomy depressed ornithine decarboxylase activity, but increas ed S-adenosylmethionine decarboxylase activity, In the neural tissue, lack of juvenile hormone depressed both ornithine decarboxylase and S- adenosylmethionine decarboxylase activities, resulting in a significan t reduction of polyamine titres, Juvenile hormone injections into alla tectomized females enhanced enzyme activities and increased polyamine titres. These findings suggest that the neural tissue, like the fat bo dy, may be a target organ for juvenile hormone action. The present dat a reveal tissue-specific patterns of polyamine metabolism and demonstr ate the action of juvenile hormone on polyamine metabolism.