Effects of cholera toxin on ornithine decarboxylase activity in mouse skin

The subcutaneous injection of cholera toxin into adult mice resulted in a sustained increase in cyclic AMP levels in mouse epidermis after a lag period of about 2 hr. An increase in ornithine decarboxylase activity occurred between 7 and 10 hr, which was maintained for at least 10 hr. The increase in decarboxylase activity was localized to the area of epidermis visually affected by cholera toxin and was unaffected by hypophysectomy, suggesting a direct effect of the toxin on the epidermal cells. The subcutaneous injection of cholera toxin also led to an increase in cyclic AMP levels in newborn mouse skin. In contrast to adult mice, newborn mouse skin contained high basal activities of ornithine decarboxylase in both the epidermal and dermal fractions. The activity in both fractions was markedly decreased following cholera toxin injection. The ability of cholera toxin to induce both epidermal and dermal ornithine decarboxylase activity developed between 10 and 21 days after birth.