ECDYSONE OXIDASE AND 3-OXOECDYSTEROID REDUCTASES IN MANDUCA-SEXTA - DEVELOPMENTAL-CHANGES AND TISSUE DISTRIBUTION

The activities of ecdysone oxidase (EO), 3-oxoecdysteroid 3alpha-reduc tase (3alpha-R), and 3-oxoecdysteroid 3beta-reductase (3beta-R) were d etermined for epidermis, hemolymph, and fat body of wandering fifth in star Manduca sexta larvae and for midguts of various developmental sta ges between 3 days after the last larval and 14 days after the pupal e cdysis. The larval midgut was the only organ showing substantial speci fic activities of EO and 3alpha-R, and both increased up to the sevent h day after ecdysis. Hemolymph and fat body had only moderate to high 3beta-R and low EO activities, and the epidermis did not contain signi ficant activity of any of the enzymes. On the ninth day after the last larval ecdysis the larval midgut epithelium was replaced by a new pup al midgut epithelium. After this event only 3beta-R was restored to hi gh activities, whereas EO and 3alpha-R showed only low to marginal act ivities. It is concluded that only the larval midgut has a role in the inactivation of ecdysteroids by 3-epimerization. (C) 1993 Wiley-Liss, Inc.