An immunocytochemical study of the proliferating cell nuclear matrix antigen p125/6.5 during rat spermatogenesis.

In previous studies of proliferating mammalian cells a p125/6.5 nuclear matrix antigen displaying a marked increase in mitotic cells has been identified. This antigen was investigated by immunocytochemistry of cryosections of testes at different stages of postnatal development: newborn, 20 days after birth and sexually mature rats. In Sertoli cells, the distribution of the p125/6.5 antigen parallels [3H]thymidine incorporation: present in newborn and absent in sexually mature testes. The p125/6.5 antigen is present also in some prespermatogonia of the newborn rat testis, which do not incorporate [3H]thymidine. At later stages of development, the p125/6.5 antigen is present also in first meiotic prophase spermatocytes displaying an extrachromosomal nucleoplasmic distribution, while absent in spermatids and spermatozoa. These results show that the p125/6.5 antigen increases not only during mitosis, but also during meiosis. They suggest further that this antigen is characteristic of both proliferating cells and cells (prespermatogonia) committed to proliferation.