Effects of methyl xanthine derivatives on cyclic AMP levels and ornithine decarboxylase activity of rat tissues

The administration of aminophylline results in rapid increases in cyclic AMP in the adrenal medulla, adrenal cortex, liver, and kidney of the rat. The injection of theophylline results in a similar increase in cyclic AMP in the liver of the rat. In all instances, these increases are followed by 4- to 2-fold elevations of ornithine decarboxylase activity. The generality of this phenomena suggests that ornithine decarboxylase activity is regulated by an increase in cyclic AMP.