DIFFERENTIATION OF PRIMARY SPERMATOCYTES TO ELONGATED SPERMATIDS BY MAMMALIAN FSH IN ORGAN-CULTURE OF TESTES FRAGMENTS FROM THE NEWT, CYNOPS-PYRRHOGASTER

Our previous studies (10, 11) showed that mammalian follicle-stimulati ng hormone (FSH) alone was indispensable and sufficient for the initia tion and promotion of spermatogenesis from secondary spermatogonia to primary spermatocytes in organ culture of testes fragments from the ne wt, Cynops pyrrhogaster. The present study demonstrated that FSH promo ted in the same model system the differentiation of primary spermatocy tes even further: to the stage of elongated spermatids. When testes fr agments, consisting of somatic cells and germ cells (mostly primary sp ermatocytes), were cultured in a control medium for three weeks, only round spermatids and spermatogonia were observed; both the diameter of the cysts and the viability of the germ cells decreased to about 10-1 5% of the original level. On the other hand, when the medium was suppl emented with FSH, elongated spermatids appeared by the second week; bo th the diameter of the cysts and the viability of the germ cells were maintained at a higher level than in the control medium. The effect of FSH was dose-dependent. However, neither transferrin, androgens (test osterone and 5 alpha-dihydrotestosterone) nor luteinizing hormone (LH) was effective. The addition or cyanoketone, a specific inhibitor of 3 beta-hydroxy-Delta(5)-steroid dehydrogenase (3 beta-HSD) (32), to the FSH-containing medium did not prevent the differentiation promoted by FSH, indicating that it is unlikely that Delta 4-steroid metabolites produced in fragments by FSH acted directly on germ cells. Insulin was found to improve the viability of germ cells during a 2 week of cultu re period. In the presence of FSH, the cells in various differentiativ e stages had morphological characteristics very similar to those in vi vo, whereas in the absence of FSH primary spermatocytes showed abnorma l features in their nuclei and cytoplasm, indicating that they were de teriorating. These results and our previous results (1-3) suggest that FSH promotes primary spermatocytes to differentiate into elongated sp ermatids probably by stimulating Sertoli cells to secrete factors whic h then act on the germ cells.