Seawater acclimation causes independent alterations in Na+/K+- and H+-ATPase activity in isolated mitochondria-rich cell subtypes of the rainbow trout gill.

Mitochondria-rich cells (MR cells) of the gills of rainbow trout undergo changes in relative distribution and biochemical function during acclimation to partial-strength (10 per thousand ) and full-strength (30 per thousand ) seawater. In isolated total gill cells, Na(+)/K(+)-ATPase activity increased fivefold and H(+)-ATPase activity decreased fourfold when trout were acclimated to either 10 per thousand or 30 per thousand seawater. When total MR gill cells were separated based on differential binding to peanut lectin agglutinin (PNA), the PNA subtypes underwent a change in relative distribution in seawater-acclimated fish. In freshwater, the ratio of PNA(-):PNA(+) was 65:35 while in seawater the distribution changed to 20:80 PNA(-):PNA(+). Additionally, differential changes in Na(+)/K(+)-ATPase and H(+)-ATPase activity in each of the independent cell types occurred during seawater acclimation; Na(+)/K(+)-ATPase activity in the PNA(-) cells increased by 197% while in PNA(+) cells Na(+)/K(+)-ATPase decreased by 57%. However, H(+)-ATPase activity was decreased in both PNA(-) (84%) and PNA(+) (72%) subtypes during acclimation to seawater.