Ornithine decarboxylase and polyamines in silkmoth pupal tissues: Effects of ecdysone and injury

Abstract

1. 1. Ornithine decarboxylase was almost undetectable in fat body and wing tissue from cecropia silkmoth pupae in diapause, but after injection of β-ecdysone, activity rose steeply to a maximum at about 18 h. Injection of water or the inactive analog 22-isoecdysone also induced the enzyme in both tissues, an effect attributable to injury, but in wings β-ecdysone induced a 10-fold greater increase. Cycloheximide blocked induction of the enzyme. 2. 2. Tissues incubated for 12–18 h in culture medium developed a certain level of ornithine decarboxylase. β-Ecdysone in the medium caused definite additional induction, while α-ecdysone had little or no effect. 3. 3. The levels of the polyamines putrescine, spermidine and spermine were determined in a series of tissue samples. Putrescine was relatively concentrated (2–8 mM) in hemolymph, and was elevated 48 h after injection of ecdysone; in fat body, levels were lower and changed less. Spermidine was elevated in fat body and wings 24–36 h after injection of β-ecdysone. Spermine showed no clear pattern of change. 4. 4. Among the consequences of ecdysone action in pupal fat body and wings, induction of ornithine decarboxylase coincides in time with a previously observed peak of RNA synthesis, and maximal spermidine levels appear somewhat later.