Fig. 4. Western blot analysis of Na⁺+K⁺-ATPase -subunit protein in partially purified plasma membrane preparations from anterior and posterior gills of Callinectes sapidus acclimated for 2 weeks to 35 or 5  salinity. Gills 3–5 (anterior) and 6–8 (posterior) from four crabs were pooled for each treatment. Following SDS–polyacrylamide gel electrophoresis and transfer to nylon membranes, -subunit protein was detected by incubation with 5 monoclonal antibody. The left-hand lane contains Kaleidoscope prestained standards with the indicated molecular masses. The data are representative of three separate experiments.