In vitro effects of juvenile hormone on puffing in Chironomys salivary glands

Isolated salivary glands of Chironomus tentons prepupae were incubated in a synthetic culture medium containing 10^?4 M β-ecdysone and various amounts of C18-Cecropia juvenile hormone (JH). After 2 or 4 h their chromosomal puffing patterns were analyzed. Between 3.4 × 10^?7 and 3.4 × 10^?5 M, JH induces the ‘juvenile’ puff I-19-A₁. At higher concentrations (3.4 × 10^?4 M), a previous induction of this puff is reversed. The ecdysone-dependent puff I-18-C becomes progressively reduced at JH concentrations above 3.4 × 10^?6 M. Wounding of glands results in a transient, JH-independent induction and reduction, respectively, of puffs I-19-A₁ and I-18-C, and eventually, in the formation of a new puff (I-19-A₂); wounding generally diminishes the effects of JH on puffing. In the absence of ecdysone, puffs I-19-A₁ and I-19-A₂ develop spontaneously, and 3.4 × 10^?4 M JH no longer reverses puff formation in I-19-A₁. These results suggest an antagonistic interaction of JH and ecdysone with a cellular regulatory circuit involving cell membrane permeability changes.