Biosynthesis and release of glycoproteins by pineal gland in organ culture

1. 1. In vitro biosynthesis of glycoproteins in neuroendocrine tissue was studied by incubating rat pineal glands with L -[3H]fucose and determining trichloroacetic acid-insoluble radioactivity. After 20 h of incubation 67% of the total trichloroacetic acid-insoluble radioactivity was in the gland and 33% had been released into the medium. Essentially all of the 3H-labelled trichloroacetic acid-insoluble material consisted of [3H]fucose-containing glycoproteins. 2. 2. Polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulfate showed a heterogeneous pattern of [3H]glycoproteins in the gland (apparent mol. wts 30 000–200 000) with several characteristic peaks. In contrast, 50% of the [3H]glycoproteins in the medium were in a single broad peak (apparent mol. wts. 30 000–70 000). 3. 3. In experiments in which glands were incubated in the presence of [3H]fucose and [14C]leucine, the ratio of 3H to 14C in macromolecules was 7 times higher in the medium than in the gland.