Distribution of ornithine decarboxylase in ovaries of rat and hamster during pro-oestrus.

The biosynthesis of polyamines is dramatically increased in the ovaries of rat and hamster during the evening of pro-oestrus. In an attempt to shed some light on the physiological function of this biosynthesis ornithine decarboxylase (ODC), which catalyzes the rate-limiting step in the biosynthesis of the polyamines, was immunohistochemically localized in the ovaries from rat and hamster during pro-oestrus. At dioestrus, only a few immunoreactive cells were found in the ovaries. During the evening of pro-oestrus, on the other hand, numerous immunoreactive cells were observed in the ovaries. These cells were confined to the internal thecal layer of Graafian as well as smaller follicles and to the interstitial tissue of the ovary. The granulosa cells appeared to be devoid of immunoreactive ODC. The hamster ovary, which during this time exhibited considerably higher levels of ODC activity than the ovaries from the rat, did accordingly contain more immunoreactive cells than the rat ovary.