DOES SPHINGOMYELIN PARTICIPATE IN SIGNAL-TRANSDUCTION IN GILL CELLS OF EURYHALIN CRABS DURING SALINITY CHANGES

In adapted Carcinus maenas, the percentage of sphingomyelin in anterio r and posterior gills is higher in seawater (SW) than in 50%SW adapted crabs. Nevertheless, the total phospholids content remains higher in posterior than in anterior gills in both media. In vivo injection of L -3(H-3)-serine to crabs showed that the incorporation of radioactivity into gill spingomyelin was lowest in crabs acclimated to or abruptly transferred to 50%SW. During the transfers, the radioactivity incorpor ated into phosphatidylcholine, phosphatidylethanolamine and phosphatid ylserine was also dependent on acclimation salinity. In vitro incorpor ation of SH-serine into gills phospholipids of adapted crabs (to SW or 50%SW) confirmed this early effect of salt. concentration of the medi um on the sphingomyelin renewal. Analysis of the long-chain bases of p urified sphingomyelin confirmed that 90-95% and 80-85% of the total ra dioactivity of the sphingomyelin was found in the sphingosine moiety i n both in vitro and in vitro experiments. Addition of 10(-3) M Amilori de to the incubation medium affects the sphingomyelin biosynthesis fro m H-3-Serine in vitro. These results are consistent with a possible ro le of sphingomyelin or/and its metabolites in the process of adaptatio n to sudden salinity changes in crustacean gills.