Effects of dietary protein content on the enzyme activities involved in taurine biosynthesis and gallbladder bile salt levels in bluegill Lepomis macrochirus

In order to investigate the influence of dietary protein concentration on taurine biosynthesis and bile salt levels in fish, bluegill Lepomis macrochirus was fed on three diets with different levels of casein for 12 days. At the end of experiment, hepatic enzyme activities involved in amino acid metabolism including taurine biosynthesis and gallbladder bile salt levels were determined. Alanine transaminase activity was significantly elevated when dietary casein level became higher, and cysteinesulfinate decarboxylase activity was decreased inversely in proportion to the dietary protein content. In gallbladder bile, the proportion of chenodeoxycholyltaurine was increased when dietary casein level became higher.