Synthesis of lipids in the fat body of Gryllus bimaculatus: Age-dependencyand regulation by adipokinetic hormone

The free abdominal fat body of adult female Mediterranean field crickets, G ryllus bimaculatus, synthesizes lipids from [1-C-14]-acetate in vitro. Up t o an age of 12 h, the incorporation of acetate into lipids is very low and then rises to a maximum 24 h after adult emergence. Thereafter, the incorpo ration of acetate decreases to moderate levels at day 2 and then slowly dec reases until day 30. The adipokinetic hormone of G. bimaculatus (Grb-AKH) s ignificantly inhibits the incorporation of acetate at a concentration of 10 (-11) M; maximum inhibition (approximately 95%) is reached at 10(-8) M. The inhibiting effect of Grb-AKH is fast, dose-dependent, and reversible. The periovaric fat body shows a similar pattern of acetate incorporation, altho ugh rates of incorporation are lower; the incorporation can be inhibited by Grb-AKH as well. The segmental abdominal fat body and the fat body from th e head both incorporate acetate into lipids at low rates that cannot be inh ibited significantly by AKH. Prepurified brain extracts significantly inhib it acetate incorporation by free abdominal fat bodies at a concentration of 0.1 brain equivalent. Allatostatins and crustacean cardioactive peptide, w hich are both present in cricket brains, are not responsible for this inhib iting effect. Octopamine causes a dose-dependent inhibition of acetate inco rporation whereas synephrine had no such effect. The inhibiting effect of G rb-AKH on the formation of lipid stores in the fat body and its consequence s for reproductive processes are discussed. Arch. Insect Biochem. Physiol. 47:198-214, 2001. (C) 2001 Wiley-Liss, Inc.