TWENTY-FOURTH ANNUAL EASTERN FISH HEALTH WORKSHOP Royal Pavilion Resort, Atlantic Beach, NC MARCH 9-11, 1999 Effects Of Hypoxia On The Respiratory Burst And Associated Bactericidal Activity Of Pronephritic Cells In The Mummichog, Fundulus heteroclitus. Kimberly A. Boleza1, Louis E. Burnett2, and Karen G. Burnett1 1Department of Microbiology and Immunology, Medical University of South Carolina and 2Grice Marine Laboratory, University of Charleston, Charleston, SC Organisms living in estuarine environments are exposed to diurnal and seasonal variations in dissolved oxygen, dissolved carbon dioxide and pH. These fluctuations are of particular concern in the southeastern United States where estuaries serve as habitats and nursery grounds for commercially and ecologically important organisms such as oysters, shrimp and fish. Circumstantial evidence suggests that these environmental variables may lower disease resistance in organisms that inhabit estuaries. We have shown that moderate levels of hypoxia and acidosis suppress the respiratory burst of phagocytic cells in the Eastern oyster, Crassostrea virginica while hypoxia enhances susceptibility to infection with the pathogen Vibrio parahaemolyticus in the grass shrimp, Palaemonetes pugio. We have demonstrated that moderately low O2, high CO2 and low pH within physiologically relevant ranges inhibits the production of reactive oxygen species (ROS) by pronephritic cells of the mummichog, Fundulus heteroclitus, as measured by luminol-enhanced chemiluminescence. Preliminary data suggest that these environmental variables also reduce bactericidal activity against the pathogen V. parahaemolyticus. To evaluate bactericidal activity, phagocytic cells were incubated with V. parahaemolyticus for specified times at which point the cells were lysed and surviving bacteria were grown to exponential phase. Bacterial growth was quantified by measuring optical density. Pronephritic cells displayed significant bactericidal activity against V. parahaemolyticus which was blocked by trifluoroperazine (TFP), a drug which inhibits the initiation of respiratory burst by NADPH oxidase. These data demonstrate that the respiratory burst mediates a major component of bacterial killing by phagocytic cells of the mummichog. Experiments are currently underway to evaluate the effects of moderately low O2, high CO2 and low pH on bactericidal activity of the respiratory burst against V. parahaemolyticus in F. heteroclitus. Supported by EPA Agreement R-826399. Return to 24th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page