Counteraction by 20‐hydroxyecdysone of the effect of juvenile hormone on phosphorylation of ribosomal protein S6

Abstract
Phosphorylation of ribosomal protein S6, induced when the fat body of Sarcophaga peregrina (flesh‐fly) larvae was incubated in vitro in the presence of 32P, was found to be suppressed by juvenile hormone. This suppressive effect of juvenile hormone was counteracted by a physiological concentration of 20‐hydroxyecdysone. Since 20‐hydroxyecdysone is known to induce phosphorylation of S6 in vivo, this reaction was suggested to be regulated by the balance of the effects of ecdysone and juvenile hormone.