Fucosylation of glycoproteins in rat spermatocytes and spermatids

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Abstract
Glycoprotein synthesis in pachytene spermatocytes and round spermatids, isolated from rat testes, was studied by analysis of the incorporation of (3H)‐fucose. The isolated germ cells were capable of incorporating (3H)‐fucose into cell‐bound, acid‐precipitable components for an incubation period of at least 23 hours (at 32°C). In young spermatids, engaged in the formation of the acrosome, (3H)‐fucose was incorporated into more than 16 different glycoproteins within the molecular weight range of 20.000–100,000. A qualitatively similar set of glycoproteins was found to be labeled in spermatocytes. Radioautography showed that after 4 hr most of the incorporated radioactivity was present at one pole in the perinuclear zone of spermatocytes and spermatids, which could reflect incorporation of fucose in the Golgi apparatus. The newly fucosylated glycoproteins were associated with a particulate subcellular fraction (membrane fraction). Trypsin treatment of whole cells after 25 hours of incubation with (3H)‐fucose, however, did not cause significant lysis of tritiated glycoproteins.From the results it was concluded that the majority of the newly fucosylated glycoproteins in spermatocytes and spermatids remained associated with an intracellular membrane system, presumably the Golgi apparatus and the vesicles that arise from this structure, to be deposited subsequently in proacrosomic granules and the acrosome. The results also suggest that initiation of the synthesis of spermatidal glycoproteins occurs during the prophase of meiosis in spermatocytes.