Effect of hexadecane on piglet epidermal ornithine decarboxylase activity

Topical application of hexadecane has been shown to induce hyperproliferation and hyperkeratosis in rodent skin. The application of hexadecane to epidermis from the backs of piglets less than 1 week old resulted in a rapid biphasic-rise in the level of ornithine decarboxylase (ODC) activity. The second phase of the elevation of activity was suppressed by cycloheximide indicating that it resulted from de novo protein synthesis. The first, cycloheximide-insensitive phase presumably represents activation of existing enzyme. The activation of this latent ODC by hexadecane was independent of extracellular calcium. A similar degree of activation was observed using the bivalent-cation ionophore A23187 which augmented the hexadecane effect implicating a rise in intracellular calcium concentration as a possible cause for the activation possibly via the receptor-mediated phospholipid hydrolysis. The time-course of the ODC activation also corresponded with a rapid fall in cAMP levels indicating a possible role for cAMP in ODC regulation.