Characterization of a broad-scope amino acid transport system in sand dollars.

Both echinoderm embryos and adults take up alpha-amino acids by an apparent broad-scope transport system. This transporter can be characterized as follows: alanine transport is not blocked by alpha-(methylamino)isobutyric acid. Leucine and other lipophilic neutral amino acids are preferentially transported. Transport is sodium dependent and blocked by 2-aminobicyclo-[2,2,1]heptane-2-carboxycylic acid. Lysine and aspartate transport is inhibited by lipophilic neutral amino acids. Taurine, a beta-neutral amino acid, is translocated via a second and independent carrier.