3-dehydroecdysone secretion by the molting gland of the cockroach, Periplaneta americana (L.)

Prothoracic glands of Periplaneta americana were tested under in vitro cond itions for their ability to release 3-dehydroecdysone (3DE) besides ecdyson e. 3DE was identified by RIA after conversion to ecdysone by a ketoreductas e-containing hemolymph preparation as well as in HPLC fractions of incubati on medium by an antiserum with affinity to 3DE and ecdysone. The ratio of 3 DE to ecdysone secreted into the culture medium was found to vary between 2 :1 and 7:1, depending on the period in the last nymphal instar. Enzyme acti vity of 3 beta-ketoreductase showed fluctuations that coincided with the he molymph ecdysteroid titre. Homogenates of prothoracic glands do not contain ecdysone but contain 3DE. Nevertheless the glands release 3DE as well as e cdysone under in vitro conditions. Different sites where conversion of 3DE to ecdysone takes place are discussed. Arch. Insect Biochem. Physiol. 41:10 7-116, 1999. (C) 1999 Wiley-Liss, Inc.