Changes in antizyme-ornithine decarboxylase complexes in tissues of hormone-treated rats

The presence of antizyme-ornithine decarboxylase complex in thymus and kidney of rats was demonstrated using the method of Y Murakami et al. [(1985) Biochem. J. 225, 689-697]. A very small amount of complex was found in kidney of control rats, accounting for only 1-3% of total enzyme in the tissue, while in thymus, approximately one-third of the total ornithine decarboxylase in thymus occurred as an antizyme-enzyme complex. After treatment with dexamethasone, both free ornithine decarboxylase and antizyme-ornithine decarboxylase decreased in thymus, the free enzyme activity decreasing more rapidly. In kidney, the concentration of the antizyme-ornithine decarboxylase complex increased after dexamethasone treatment, but only after the induction of free enzyme activity had reached its peak and begun to decrease. The pattern of the changes in amount of antizyme-ornithine decarboxylase complex after prolactin treatment differed from those observed in the dexamethasone-treated animals. In both kidney and thymus, the concentration of antizyme-ornithine decarboxylase complex increased concurrently with the induction of free enzyme activity. Both free and complexed ornithine decarboxylase had increased at 2.5 h after prolactin treatment and continued to increase to maximum specific activities at similar rates. In thymus, the amount of ornithine decarboxylase present as a complex reached 70% of the total in the tissue. In both thymus and kidney, the concentration of antizyme-ornithine decarboxylase complex decreased more slowly than did free enzyme activity. Free antizyme was observed only in thymus of dexamethasone-treated animals. The amount of measurable inhibitor was decreased if cycloheximide was given with dexamethasone.