Mammalian follicle-stimulating hormone stimulates DNA synthesis in secondary spermatogonia and Sertoli cells in organ culture of testes fragments from the newt,Cynops pyrrhogaster

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Abstract
We previously showed in organ culture of testes fragments from Cynops pyrrhogaster that mammalian folicle-stimulating hormone (FSH) stimulates secondary spermatogonia to differentiate into primary spermatocytes. In this report, we demonstrate in organ culture that FSH stimulates DNA synthesis in secondary spermatogonia and Sertoli cells: the numbers of secondary spermatogonia and Sertoli cells incorporating 5-bromo-2′ -deoxyuridine (BrdU)throughout the culture period in the presence of FSH were 3-5 times those incorporating BrdU in the absence of FSH. Moreover, addition of FSH, induced after a day a remarkable increase in the number of spermatogonia and Sertoli cells incorporating BrdU. The above results indicate that FSH stimulates and induces DNA synthesis in spermatogonia and Sertoli cells. Most of the spermatogonia within a cyst were labelled simultaneously and at the same density, indicating that they underwent synchronous DNA synthesis, whereas all the Sertoli cells within a cyst were not labelled simultaneously, indicating that they synthesised DNA asynchronously. When testes fragments pulse-labelled with Brdu were cultured in FSH for 14 days, the secondary spermatogonia differentiated into primary spermatocytes, whereas in the absence of FSH they failed to differentiate and most died by the 7th day. The above results together show that FSH is required for the proliferation of both secondary spermatogonia and Sertoli cells as well as the differentiation of secondary spermatogonia into primary spermatocytes.