Effect of calcium on amino acid and dipeptide transport by intestines of American lobster ( Homarus americanus ) and Atlantic white shrimp ( Litopenaeus setiferus ) (908.6)

Previous work using L‐histidine and zinc in American lobster intestine has shown these solutes can be transported as bis‐complexes (Histidine‐Zinc‐Histidine) across the intestine using a peptide transporter. Furthermore, transport of L‐leucine has been shown to be inhibited by high calcium concentrations. Dipeptide and bis‐complex transport and the role of calcium were investigated in the perfused intestine of lobster and Atlantic white shrimp. Samples of serosal medium were analyzed for amino acid composition by gas chromatography. In lobster, the transport of glycylsarcosine (Gly‐Sar) from mucosal to serosal medium was measured for a range of pH values and either 0.5mM or 25mM calcium chloride. The rate of Gly‐Sar transport was stimulated two‐fold with pH 8.5 in the lumen. Reduced calcium chloride concentration stimulated Gly‐Sar transport two‐fold. In shrimp, the transport of L‐histidine from mucosal to serosal medium was measured. The addition of 50µM zinc chloride increased the rate of histidine transport, while Gly‐Sar inhibited transport. The rate of histidine transport was significantly higher with 1mM calcium chloride than with 25mM. These results indicate that shrimp transport bis‐complexes in a manner similar to lobster, which is inhibited by the presence of a competing dipeptide. High calcium concentration has an inhibitory effect on both amino acid and dipeptide transport. Grant Funding Source : Supported by USDA Agricultural and Food Research Initiative Competitive Grant no. 2010‐65206‐20617