Variations in intracellular choline levels may account for differences in glycine betaine synthesis between conspecific oyster populations responding to hyperosmotic stress

Abstract

Oysters (Crassostrea virginica) from the Atlantic coast use large intracellular 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 change 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 measured the intracellular concentration of choline in both groups of oysters following adaptation to both low and high salinity, using a high-performance liquid chromatographic protocol. The choline concentrations in gill tissue from Atlantic and Bay oysters are similar following low salinity acclimation and similar to Bay oysters in the field. However, following high salinity acclimation, the intracellular choline pool increases substantially in Atlantic oysters, while declining slightly 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 amino acids. J. Exp. Zool. 278:283–289, 1997. © 1997 Wiley-Liss, Inc.