Cyclic GMP production and excretion by Drosophila cells: Modulation by 20-hydroxyecdysone

Intracellular and extracellular concentrations of cyclic GMP were measured under different conditions in cultures of two 20-hydroxyecdysone sensitive clones of Drosophila melanogaster. Exponentially growing cells maintained a concentration of 0.15 pmol/10⁶ cells inside the cells (about 10⁻⁶ M) and 5 pmol/10⁶ cells in the medium. When the medium was changed equilibrium was restored in the cells in about 15 hr. Addition of 20-hydroxyecdysone arrested growth and induced several enzymes and morphological modifications. It also increased (up to 10-fold) both intracellular and extracellular cyclic GMP levels depending on the amount of hormone. The ratio of the two levels remained constant.