Juvenile hormone production, juvenile hormone esterase, and juvenile hormone acid methyltransferase in corpora allata of Manduca sexta

Juvenile hormone (JH) secretion by corpora allata (CA) of last instar larvae of Manduca sexta was studied by measuring the rate of JH synthesis in vitro with a radiochemical assay and by analyzing JH esterase and JH acid methyltransferase (JHAMT) activities in CA. CA of 0‐day (0–12 hr after ecdysis), 4‐day (early wandering larvae), and 7‐day (prepupae) animals were used in this study. CA of 0‐day larvae showed high rates of JH synthesis, whereas CA of both 4‐and 7‐day animals did not produce detectable amounts of radiolabeled JH. JH esterase activity was absent in 0‐day CA, but high activity was present in both 4‐ and 7‐day CA. However, incubation of older CA in medium containing a potent JH esterase inhibitor did not yield radiolabeled JH, indicating that these glands are unable to methylate JH acids. This conclusion is supported by the observations that JHAMT activity was high in 0‐day CA, but absent from older CA. In view of the reported peak of JH in the hemolymph on day 7, an alternative means for producing JH is postulated.