VARIATIONS IN INTRACELLULAR CHOLINE LEVELS MAY ACCOUNT FOR DIFFERENCES IN GLYCINE BETAINE SYNTHESIS BETWEEN CONSPECIFIC OYSTER POPULATIONS RESPONDING TO HYPEROSMOTIC STRESS

Oysters (Crassostrea virginica) from the Atlantic coast use large intr acellular concentrations of glycine betaine as an osmolyte to respond to hyperosmotic stress. In conspecific oysters from the Chesapeake Bay , intracellular concentrations of glycine betaine are low and do not c hange in response to high salinity stress. One possibility to explain this difference is that the availability of choline, the precursor of glycine betaine, is different in the two groups of oysters. We have me asured the intracellular concentration of choline in both groups of oy sters following adaptation to both low and high salinity, using a high -performance liquid chromatographic protocol. The choline concentratio ns in gill tissue from Atlantic and Bay oysters are similar following low salinity acclimation and similar to Bay oysters in the field. Howe ver, following high salinity acclimation, the intracellular choline po ol increases substantially in Atlantic oysters, while declining slight ly in Bay oysters. In addition to these results, we present a detailed protocol for measuring choline in tissues of marine organisms, where the analysis is complicated by the presence of high salts and free ami no acids. (C) 1997 Wiley-Liss, Inc.