Hypoxia-induced changes in the zebrafish (Danio rerio) skeletal muscle proteome

In this study, patterns of protein expression in zebrafish (Danio rerio) white skeletal muscle after 48 h exposure to hypoxia (P(O2)=1.9 kPa) or normoxia (P(O2)=18.6 kPa) were evaluated using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE). Proteins were separated over two pH ranges in the first dimension (pH 4-7 and pH 7-11) prior to separation in the second dimension, resolving a total of 821 protein spots. Of these, 77 spots (9.4%) differed between hypoxia and normoxia (p ≤ 0.01), with approximately twice as many proteins being higher during hypoxia (56) compared to the number found to be higher in normoxic fish (26). Thirty-one protein spots were identified by MALDI-TOF/TOF mass spectrometry. The expression of several glycolytic enzymes was greater in hypoxia than in normoxia, whereas enzymes associated with mitochondrial ATP synthesis were lower during hypoxia. Among the more highly up-regulated proteins during hypoxia were two variants of hemoglobin α subunit. These patterns of protein expression are consistent with a hypoxic response that enhances anaerobic metabolism and O(2) transport to tissues, with a concomitant suppression of mitochondrial metabolism. These proteomic changes may contribute to the acclimation of zebrafish to hypoxia, thereby increasing their tolerance of low oxygen concentrations.