Formation of phosphatidylethanolamine as a putative regulator of salt transport in the gills and esophagus of the rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) adapted to brackish water (BW) showed 32P-phospholipid patterns in gill and esophagus tissues dominated by phosphatidylcholine (PC) when the fish were incubated in vivo either in fresh water (FW) at 5, 16°C or in BW at 5°C, and corresponding patterns dominated by phosphatidylethanolamine (PE) when the fish were incubated in vivo either in seawater (SW) at 5, 16°C or in BW at 16°C, in both cases with (32P) phosphate as the precursor labeling the polar headgroups.

Equivalent incorporations in the same fish with (114C) acetate as precursor, labeling the lipophilic moiety, showed 14C-phospholipid patterns in gill and esophagus tissues dominated by PC, practically independent of ambient salinity and temperature. Eels (Anguilla anguilla) similarly incubated in vivo in FW at 18°C showed 32P-phospholipid patterns in gill tissue dominated by PE after preadaptation to either FW or SW; corresponding patterns after preadaptation to BW showed PE = PC.

We suggest that PE participates in a stabilization of the integral membrane proteins that regulate the function of apical ion channels. The absence of PE dominated 32P-phospholipid patterns in FW after preadaptation to isosmotic BW would indicate that the fish do not experience an osmotic challenge under these circumstances.