The effect of prolonged anoxia on enzyme activities in oysters (Crassostrea virginica) at different seasons

The effect of prolonged anoxia (96 h under a N-2 atmosphere) during either winter (November) or summer (July) was investigated by measuring the maxima l activities of 20 metabolic enzymes in gill, mantle, hepatopancreas, and p hasic and catch adductor muscles of the oyster, Crassostrea virginica. The enzymes analyzed are involved in carbohydrate and amino acid metabolism, th e pentose phosphate shunt, anaplerotic reactions of the TCA cycle, and phos phagen/adenylate metabolism. The data demonstrate that oyster metabolism is influenced by both long-term seasonal change and by shorter-term environme ntal insult (anoxia). Seasonal changes were concentrated among enzymes invo lved in glycogen metabolism whereas the prominent response to anoxia was su ppression of PK activity. Anoxia exposure induced tissue-specific changes i n enzyme activities suggesting a substantial metabolic reorganization invol ving both coarse controls on enzyme amount and reversible covalent modifica tion. In addition, the effects of anoxia on enzymes of intermediary metabol ism were seasonally dependent and more widespread in the winter. These resu lts demonstrate the interaction of two environmental variables (season, ano xia) and suggest the importance of season as a modifying factor in the anox ic response. (C) 1999 Elsevier Science B.V. All rights reserved.