THE INFLUENCE OF SALINITY ACCLIMATION ON FREE AMINO-ACIDS AND ENZYME-ACTIVITIES IN THE INTESTINAL-MUCOSA OF RAINBOW-TROUT, ONCORHYNCHUS-MYKISS (WALBAUM)

Postprandial changes of Arg, Leu, Val, Ala, Asp, Glu, Gly, Pro and Tau as well as activities of three enzymes of the transdeamination system in the midgut mucosa and, for comparison, in the liver of freshwater and seawater acclimated Oncorhynchus mykiss were studied. In the mucos a a postprandial increase of Arg, Leu, Val, Ala, Asp, Glu, Gly and Pro occurred. In contrast, only the postprandial Arg level increased stro ngly in the liver. Levels of Leu, Val, Ala, Asp, Glu, Gly, Pro and Tau remained stable. Concentrations of Ala, Asp, Glu and Pro are higher i n the liver than the mucosa. Tau is the most important osmotic effecto r in both organs, but its concentration is much lower in the liver. It s postprandial concentrations remained stable in both tissues but were significantly higher in seawater trout. The trend of a stronger postp randial rise of Arg, Leu, Val, Ala, Asp, Glu, Gly and Pro levels in se awater trout than in freshwater trout was shown. In mucosa tissue aspa rtate aminotransferase activities were higher in seawater trout. Ratio s of aspartate aminotransferase, alanine aminotransferase and glutamat e dehydrogenase are similar to those of the gills. Copyright (C) 1996 Elsevier Science Inc.