Proliferation of mouse primordial germ cells in vitro: a key role for cAMP.

Two agents known to enhance the level of intracellular cAMP (dibutyryl cAMP and forskolin) markedly increase the number of 8.5, 10.5, and 11.5 days postcoitum (dpc) mouse primordial germ cells (PGCs) cultured on TM4 cell feeder layers. Forskolin (FRSK) caused a significant increase of PGC number also in monodispersed cell suspensions obtained from PGC-containing tissues of the three embryonic ages studied and in purified 11.5 dpc PGCs cultured without feeder layers. The addition to the culture medium of adenosine-3',5'-cyclic monophosphorothioate RP isomer (Rp-cAMPS, a competitive antagonist for cAMP-dependent protein kinases), significantly reduced the effects of FRSK. Last, FRSK stimulated PGC proliferation, as assessed by 5-bromo-2'-deoxyuridine incorporation. We conclude that cAMP-dependent mechanisms play a crucial role in the control of mitotic proliferation of mouse PGCs in culture.