frozen at −80 °C. Plasma was separated after centrifugation at
10,000×g for 5 min and frozen at −80 °C. Gill filaments were
placed in SEI buffer (150 mM sucrose, 10 mM EDTA, 50 mM
imidazole, pH 7.3), flash frozen in liquid nitrogen, and stored at
−80 °C until analysis.
2.3. Analyses
Plasma osmolality was measured using a vapor pressure
osmometer (Wescor 5100C, Logan, UT, USA). Na+, K+-
ATPase activity in the gill was measured as described by
McCormick (1993). Protein content was measured using a