The role of lysine-rich proteins in the acute steroidogenic response of rat adrenal cells to ACTH.

The possibility that a lysine-rich protein was involved in the acute stimulation of steroidogenesis by ACTH was investigated using [3H] labelled lysine and isolated adrenal cells. The results demonstrated that cycloheximide inhibited steroidogenesis in a dose-dependent, rapid fashion and inhibited the incorporation of radioactive lysine into protein. However cells incubated in a lysine-free medium showed the same response to ACTH as cells incubated in a lysine-containing medium. It was also demonstrated that ACTH had no effect on the incorporation of tritiated lysine into the protein or small peptide fractions. These observations suggest that a rapidly synthesised, lysine-rich protein is not involved in the acute response to ACTH.