REACTIVE OXYGEN INTERMEDIATE PRODUCTION BY OYSTER HEMOCYTES EXPOSED TO HYPOXIA

John N. Boyd

A thesis submitted to the Graduate Faculty of the University of Charleston, South Carolina in partial fulfillment of the requirement for the Degree of Master of Science

ABSTRACT
Oysters are frequently exposed to severely hypoxic conditions, especially during summer months. During the summer, there are also large numbers of disease related oyster mortalities. This research was conducted to determine if exposure to environmental hypoxia reduces the ability of oyster hemocytes to produce Reactive Oxygen Intermediates (ROI), an important part of their defense system. Oysters of the species Crassostrea virginica were held in normoxic (Po₂ = 20.0-20.7 kPa, pH = 7.8-8.0) and hypoxic conditions (Po₂ = 4.0-6.7 kPa, pH = 7.1-7.4). In vivo hemolymph variables (Po₂, Pco₂ and pH) were measured after both one hour and two days in each treatment to determine the appropriate environment for subsequent hemocyte experiments. Reactive oxygen intermediate production by hemocytes was measured using luminol enhanced chemiluminescence (CL). During CL tests, hemocytes were held under the following conditions: air (Po₂ = 20.7, Pco₂ < 0.07, pH = 7.6), hemolymph conditions in normoxic oysters (Po₂ = 5.2, Pco₂ = 0.27, pH = 7.6), and hemolymph conditions in hypoxic oysters (Po₂ = 1.47, Pco₂ = 0.53, pH = 7.1). Production of ROIs under hypoxic conditions was 33% of that under normoxia. This decrease in ROI production was the result of specific and independent effects of lower oxygen levels and decreased pH. It was not due to any direct effect of CO₂.

Published:
Boyd, J. N. and L. E. Burnett.  1999.  Reactive oxygen intermediate production by oyster hemocytes exposed to hypoxia.  J. Exp. Biol. 202:3135-3143.