Effect of salinity stress on respiratory metabolism, glycolysis, lipolysis, and apoptosis in Pacific oyster (Crassostrea gigas) during depuration stage

BACKGROUND Depuration is an important process performed to ensure the safety of oyster consumption, and the effect of salinity stress on physiological and ecological characteristics of oyster remains unknow. In this study, the simulated depuration of Crassostrea gigas was performed with the salinities varying from +/- 10% to +/- 20% away from that of production area (26, 28, 32, 35, and 38 g L-1), as well as respiratory metabolism, glycolysis, lipolysis, and apoptosis were analyzed. RESULTS (i) The oxygen consumption rate, ammonia discharge rate and enzyme activities related to respiratory metabolism were decreased significantly at salinities of 38 g L-1, indicating that salinity stress triggered the abnormal respiratory metabolism of C. gigas, further, glycolysis was enhanced. (ii) Glycogen decomposition, lactic acid increase, and fatty acid composition modifications were caused by adenosine monophosphate (AMP)-activated protein kinase (AMPK) -mediated during salinity stress. (iii) There was a clear decrease of the condition index and meat yield of C. gigas after 72 h of depuration, especially in salinity 38 g L-1. (iv) Salinity stress would lead to the increase of cytochrome c levels, then cause apoptosis of C. gigas, while heat shock protein 70 (HSP70) would interfere with this process. CONCLUSION Salinity stress had a significant effect on the physiological and ecological response of C. gigas during the depuration process, including respiratory metabolism, glycolysis, lipolysis, and apoptosis. In general, the low depuration salinity fluctuation (+/- 10%) is helpful to maintain quality of C. gigas, as well as the optimal depuration time was 48 h. (c) 2021 Society of Chemical Industry.