Tissue enzyme changes in air-exposed American eels.

Abstract

American eels (Anguilla rostrata) are known to leave the water for excursions onto land despite lacking specialized air breathing organs. Other studies have established that the eel suffers from acidosis and hypoxemia as a result of this air exposure, but the survival of the eels despite these conditions demonstrates a large degree of tolerance to these effects. This thesis will investigate the changes in tissue enzymes of the American eel as a result of air exposure. It is the hypothesis of this experiment that conditions of air exposure eels will undergo a metabolic reorganization including an initial Pasteur effect and metabolic depression indicated by changes in enzyme activities and metabolite concentrations. Eels were air exposed for 3, 5 or 10 days in boxes ensuring constant temperature and humidity. Maximal activities were determined in white muscle, gill and posterior kidney tissues harvested immediately following the particular air exposure period; as a result of technical difficulties, liver was unavailable for study. Enzymes assayed included those key in glycolysis (PFK, PK, LDH), glycogen metabolism (GPase and GSase) and gluconeogenesis (GDH, AspAT, AlaAT, and PEPCK). In addition, kinetic analysis was undertaken for PFK and PK in harvested posterior kidney. Blood collected at the time of harvest was analyzed for glucose, lactate and cortisol to determine circulating levels. Muscle samples were also analyzed for glycogen content. Although changes in enzyme rates, enzyme kinetics and metabolites were observed to result from the air exposure, it could not be concluded that the changes were part of a concerted metabolic depression.