Decarboxylation of ornithine and adenosymethionine in rat ovary during pregnancy.

The activities of L-ornithine decarboxylase (EC 4.1.1.17) and S-adenosyl-L-methionine decarboxylase (EC 4.1.50) fluctuate markedly in rat ovary during the normal oestrous cycle. Ovarian ornithine and adenosylmethionine decarboxylases also showed profound changes during pregnancy of the rat. Both enzyme activities were remarkably low in the ovary through the first 11 days of pregnancy, but sharply increased at the time the placenta is formed in the rat. The enzyme activities remained elevated almost until term. It appears that the stimulated of polyamine synthesis in rat ovary, as reflected by the enhanced decarboxylation of ornithine and adenosylmethionine, is associated with the growth of the ovarian tissue rather than the secretory function of the corpus luteum during pregnancy.