Abstract: To investigate the PI3K/AKT/GSK-3β signaling pathway in fish cold regulatory mechanism, three fish species, including tilapia (Oreochromis niloticus), zebrafish (Danio rerio) and grass carp (Ctenopharyngodon-idellus), were exposed to the cold temperature (8℃). They were reared at a common temperature (28℃) but had different cold tolerance (grass carp > zebrafish > tilapia).The expression of protein in the PI3K/AKT/GSK-3β pathway were examined. Results showed that the swimming performance decreased in turn: grass carp, zebrafish and tilapia. In tilapia, the expression of p-PTEN was decreased at cold temperature, whereas the expression of AKT, p-AKT(Ser 473) and p-GSK-3β(Ser 9) was increased at 8℃. Both in zebrafish and in grass carp, the expression of AKT, p-AKT(Ser 473) was repressed at 8℃, whereas the expression of p-GSK-3β(Ser 9) was induced at 8℃. Although the expression of p-GSK-3β(Ser 9) was commonly induced at cold temperature, and the increased abundance varied in the three fish species. The induction of p-GSK-3β(Ser 9) at 8℃ in tilapia was more significantly than that in other two fishes. PI3K/AKT/GSK-3β signaling pathway is involved in cold response and whose regulation vary in the fish species, which may contribute to the various cold tolerance of fishes.

Key words: cold stress, fishes, AKT, GSK-3β, signal pathway