EVIDENCE THAT FREE FATTY-ACIDS IN TROPHOCYTES OF PERIPLANETA-AMERICANA FAT-BODY MAY BE REGULATED BY THE ACTIVITY OF PHOSPHOLIPASE A(2) AND CYCLOOXYGENASE

Previous studies have shown that palmitic, stearic, oleic and linoleic acid levels in trophocytes prepared from the fat body of male Peripla neta americana are increased following treatment of the cells with hyp ertrehalosemic hormone (HTH), Melittin, an activator of phospholipase A(2), mimicked the action of HTH by increasing the free fatty acid con tent in a concentration-dependent manner, The increase caused by HTH c ould be eliminated by pretreatment of the trophocytes with 1 mM 4'-bro mophenacyl bromide (BPB), an inhibitor of phospholipase A,, BPB also d ecreases the concentration of free fatty acids in trophocytes not trea ted with HTH but by a smaller margin, Nordihydroguaiaretic acid (NDGA) and indomethacin, inhibitors of lipoxygenase and cyclooxygenase, resp ectively, eliminated the increase in free fatty acids evoked by HTH, I n the absence of HTH both inhibitors increased the free fatty acid con tent of the trophocytes, an effect consistent with the known mode of a ction of these agents, None of the inhibitors tested, all of which blo cked HTH activated trehalose synthesis, prevented activation of phosph orylase by HTH. This is taken as evidence that other downstream sites are also important in the regulation of trehalose production by the fa t body, It is suggested that the increase in free fatty acids evoked b y HTH, or metabolites of those fatty acids, may regulate the synthesis and release of trehalose from the trophocytes because of potential ef fects on trehalose phosphate synthase, trehalose 6-phosphate phosphata se, and the trehalose transport mechanism in the trophocyte membrane, (C) 1997 Elsevier Science Ltd.