Involvement of adipokinetic hormone in the homeostatic control of hemolymph trehalose concentration in the larvae of Bombyx mori

Prior to wandering, 5th instar larvae of the silkworm, Bombyx mori, maintai n constant hemolymph titers of trehalose, Head ligation of day 3, 5th insta r larvae significantly decreased the hemolymph trehalose concentrations, bu t the concentrations did not decrease in starved larvae. After being dilute d by replacement of larval hemolymph with insect Ringer's solution, the tre halose concentrations recovered the initial levels in 90 min in the non-lig ated larvae, while they were not restored in 90 min in the neck-ligated lar vae. These results suggest that a head factor(s) with hypertrehalosemic act ivity is involved in the homeostatic control of hemolymph trehalose concent ration. When adipokinetic hormone (AKH) was injected into neck-ligated larv ae, the trehalose concentrations increased in 2 h and decreased thereafter. Repeated injections of AKH every 4 h maintained the concentrations for 12 h. These findings suggest that AKH induces a hypertrehalosemic response and is involved in the homeostasis of hemolymph trehalose concentration in the larval feeding period. Arch. Insect Biochem. Physiol. 45:156-165, 2000. (C ) 2001 Wiley-Liss, Inc.