STUDIES ON THE ISOLATED ISLET TISSUE OF FISH. IV. IN VITRO INCORPORATION OF C14- AND H8-LABELED AMINO ACIDS INTO GOOSEFISH ISLET TISSUE PROTEINS

1. Goosefish islet tissue, incubated in vitro with C14- or H3-labeled amino acids showed significant labeling of the protein fractions. 2. The purified alcohol-soluble fraction is presumed to contain the insulin which is synthesized in vitro. 3. The rate of amino acid incorporation into the alcohol-soluble fraction increases progressively with increasing time of incubation; it is decreased in the absence of oxygen. 4. The addition of glucose decreases the number of counts incorporated into the alcohol-soluble fraction. 5. In the C14-amino acid incorporation experiments, the specific activity of the purified alcohol-soluble fraction (128,000 cpm/mg. protein) is three times greater than that of the trichlor-precipitable protein residue. 6. These studies Support the thesis that amino acids, added to the islet tissue in vitro, are incorporated into insulin.