Enhancement of ovulation in the rat by DL-alpha-difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase.

Spontaneously cycling Sprague-Dawley Rats were treated with the irreversible ornithine decarboxylase (ODC) inhibitor DL-alpha-difluoromethylornithine (DFMO) on the day of proestrus. This treatment completely suppressed both the rise in ovarian ODC and the associated increase in putrescine concentration and increased the number of eggs released the next day by 91%. At the next oestrus (5 days after DFMO) there was a increase of 53% but at the third oestrus after DFMO (9 days) there was no significant change in the number of eggs released. A model is proposed in which ornithine decarboxylase forms part of a local inhibitory feed-back system controlling the number of follicles which develop to maturity and rupture during each cycle.