Contragestational profile of the tumor-inhibiting agent, L-alanosine, in the rat and the hamster.

L-Alanosine [L-2-amino-3(N-hydroxy-N-nitrosamino)propionic acid], a tumor-inhibiting agent, induces pregnancy arrest after single or multiple SC or PO administration to rats and hamsters. Its contragestational effects are dose- and route-dependent, with no important differences in species-sensitivity or administration schedules. L-Alanosine is maximally effective shortly (3-4 days) after implantation. Both placenta and fetus appear to be target tissues. Consistent with previous in vitro findings, adenine but not aspartic acid counteracts the contragestational action of L-alanosine. The 'contragestational test', i.e., the effect on conceptus growth, appears to be an interesting approach for learning more about the antiproliferative activity of an antineoplastic agent.