Senior Theses 2003
Ashley Barabas (2003). Effect of chloride on glucose
regulation in marine crustaceans
Faculty advisor: David Scholnick
Animals must maintain stable blood glucose levels in order to survive. In most animals, glucose-6-phosphatase (G-6-Pase) is the key enzyme involved in the export of cellular glucose. Although glucose regulation in vertebrates is well understood, the effectors involved in the release of glucose from the hepatopancreas of marine crustaceans remain relatively unstudied. This study examined the influence of chloride on G-6-Pase activity in marine decapod crustaceans that regularly experience large fluctuations in environmental chloride concentrations. G-6-Pase activity was examined in the ion-regulating stone crab, Menippe mercenaria, and ion-conforming spider crab, Libinia dubia. Sensitivity of G-6-Pase to long term exposure to chloride was determined in crabs acclimated to 20 and 45 ppt. Increasing chloride stimulates hepatopancreas G-6-Pase activity and glucose export in marine crustaceans. Average G-6-Pase activity increased over two times in M.mercenaria and three times in L. dubia. Glucose export from isolated hepatopancreas increased two times after exposure to increasing chloride concentrations. These results were opposite of what has been seen in vertebrate G-6-Pase, which is inhibited by chloride. Crabs acclimated to high salinity were insensitive to changes in chloride, thereby decreasing G-6-Pase activity by approximately half. These results suggest that glucose export in marine crustaceans is stimulated and regulated by environmental chloride. Chloride activation of G-6-Pase may be an important mechanism for meeting metabolic demand in crustaceans living in ion-variable environments.