Early developmental profile of ornithine decarboxylase in the frog, Microhyla ornata and its regulation by polyamines

Ornithine decarboxylase (ODC) activity and polyamine levels were measured during early development of the frog, Microhyla ornata. ODC activity was found to be high and it showed three major peaks during the first 60 hr of development. Putrescine and spermidine levels increased gradually during the above period with little change in spermine. Treatment of developing embryos with exogenous putrescine and spermidine prevented the normal increase in ODC activity. Spermine did not have any significant effect. Addition of ornithine also prevented the increase in ODC activity. Experiment using exogenous ornithine and alpha-methylornithine revealed that formation of putrescine and/or spermidine from ornithine is necessary for the suppression of ODC to occur. Suppression of ODC takes place even if conversion of putrescine to spermidine is blocked, indicating that putrescine, independent of its conversion to spermidine, also plays a role in ODC regulation.