Seasonal variation in the antioxidant defence systems of gill and digestive gland of the blue mussel, Mytilus edulis

Seasonal variation in the level of glutathione (GSH) and in the activities of glutathione S-transferase (GST; EC 2.5.1.18), GSH-peroxidase (EC 1.11.1.9) and catalase (EC 1.11.1.6) in both the gill and digestive gland of the blue mussel (Mytilus edulis) sampled from Cork harbour were evaluated. GSH peroxidase activities are generally lowest in the period February-April. Catalase activity did not vary greatly over the year in the two tissues studied from two separate sampling sites. Levels are generally lower in the period December-April than in May-July. GSH levels fluctuated in both tissues with lowest levels occurring during the winter period. GST activity increases in the period September-March in gill tissue but does not vary significantly in digestive gland where levels are consistently lower. This enzyme may therefore carry out a tissue-specific role in protecting gill tissue against oxidative stress in winter.