POSSIBLE EXISTENCE OF NA-COUPLED AMINO-ACID-TRANSPORT IN THE PIGMENTED RABBIT CONJUNCTIVA()

The objective of the present study was to determine whether Na+-amino acid cotransport contributed to the short-circuit current (I-SC) in th e isolated pigmented rabbit conjunctiva. Glycine, L-arginine, D-argini ne, and L-glutamic acid were the amino acids tested, and bioelectric m easurements were made in the Using chamber. The I-SC was increased fro m 4% (L-glutamic acid) to 44% (L-arginine). The EC(50) was 0.35 mM for glycine, 0.06 mM for L-arginine, 0.16 mM for D-arginine, and 1 mM for L-glutamic acid. No elevation in I-SC was seen in the absence of Nain the mucosal bathing fluid. The above findings are consistent with t he possible existence of a Na+-amino acid cotransport process on the a pical side of the pigmented rabbit conjunctiva.