20‐hydroxyecdysone and juvenile hormone influence tyrosine hydroxylase activity in Drosophila females under normal and heat stress conditions

Abstract

The effects of exogenous 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the tyrosine hydroxylase (TH), the first and rate-limiting DA biosynthetic enzyme, has been studied in young females of wild type D. virilis and D. melanogaster under normal conditions and under heat stress (38 degrees C). Both 20E feeding of the flies and JH application led to a substantial rise in TH activity. A rise in JH and 20E levels was found not to prevent the response of TH to heat stress, but to change the intensity of its response to the stress exposure. Putative mechanisms of regulation of DA level by 20E and JH in Drosophila females are discussed.