Effect of brevetoxin on P-glycoprotein activity in oysters, Crassostrea virginica

It has been hypothesized that P-glycoprotein (P-gp) acts as an important protective mechanism for aquatic organisms against natural and anthropogenic stressors. In previous studies, P-gp levels in gill tissues of southeastern oysters (Crassostrea virginica) were determined monthly at an unpolluted site over a 1 year period. Higher P-gp expression was observed in the warmer months, and lower expression in the colder months. Higher expression could be associated with increases in algal toxins during the summer months. One potential natural stressor is brevetoxin, the toxic derivative from the red tide dinoflagellate Gymnodinium breve. The majority of documented G. breve blooms originate in the late summer, corresponding to maximal P-gp expression. Using rhodamine transport studies, purified brevetoxin exposure decreased p-gp activity in oyster embryos and isolated gill cells in a manner similar to verapamil, suggesting its role as a substrate of oyster P-gp. These studies suggest that P-gp expression may be an important adaptive mechanism to natural biotoxin stressors in C. virginica.