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 tissues (muscle and hepatopancreas) in two decapod crustacean species, Nephrops norvegicus and Carcinus maenas. The possibility that receptors to CHH are coupled to an elevation of cytosolic Ca2+ derived from intracellular stores via activation of the phosphatidylinositol pathway was investigated. Using an inositol 1,4,5-trisphosphate (InsP3)-specific competitive binding assay, measurable levels of InsP3 were detected in hepatopancreas and muscle in both N. norvegicus and C. maenas. Incubation of these tissues in the presence of sinus gland extracts (two sinus gland equivalents) consistently increased InsP3. In addition, Carcinus CHH (10 nM) increased InsP3 levels in Carcinus hepatopancreas and muscle. Incubation of hepatopancreas from both species in 10 mM lithium saline increased basal levels of InsP3, suggesting a significant turnover of phosphoinositides in this tissue.