ENDOCRINE REGULATION OF THE PHOSPHATIDYLINOSITOL PATHWAY IN THE NORWAY LOBSTER, NEPHROPS-NORVEGICUS, AND THE SHORE CRAB, CARCINUS-MAENAS

The present study examines the mode of action of eyestalk factors, in particular crustacean hyperglycaemic hormone (CHH), on known target ti ssues (muscle and hepatopancreas) in two decapod crustacean species, N ephrops norvegicus and Carcinus maenas. The possibility that receptors to CHH are coupled to an elevation of cytosolic Ca2+ derived from int racellular stores via activation of the phosphatidylinositol pathway w as investigated. Using an inositol 1,4,5-trisphosphate (InsP(3))-speci fic competitive binding assay, measurable levels of InsP(3) were detec ted in hepatopancreas and muscle in both N. norvegicus and C. maenas. Incubation of these tissues in the presence of sinus gland extracts (t wo sinus gland equivalents) consistently increased InsP(3). In additio n, Carcinus CHH (10 nM) increased InsP(3) levels in Carcinus hepatopan creas and muscle. Incubation of hepatopancreas from both species in 10 mM lithium saline increased basal levels of InsP(3), suggesting a sig nificant turnover of phosphoinositides in this tissue. (C) 1996 Academ ic Press Inc.