ARTICLES

Uptake of amino acids by islet of Langerhans and other tissues of the toadfish

The uptake of injected radioactive amino acids by the isolated islet and other tissues of the toadfish has been examined. The islet and most other tissues appear to actively transport most amino acids and, of the tissues studied, the islet is one of the most active in this regard. Most tissues accumulated the dicarboxylic acids to the greatest extent, with the basic amino acids and the neutral amino acids with unbranched side chains also being taken up well. However, each tissue showed a unique pattern of uptake of the different amino acids, and islet was distinguished by its high uptake of glycine 15 min after injection. The pattern of uptake of amino acids by toadfish islet does not appear to be related to their relative ability to stimulate insulin release from islets of other species or to their relative rates of metabolism, but does correlate well with the content of free amino acids in mouse islets and with the sum of the amino acid contents of anglerfish proinsulin and proglucagon.