Biochemistry: The Chemical Reactions of Living Cells, Volume 3 - D. Metzler 1980

Cell Growth, Differentiation, and Chemical Communication
Hormones
Insect Hormones

The neuroendocrine system of invertebrates and mammals has much in common. For example, insects synthesize A number of Neuropeptides [14]. One of them—the activation hormone—regulates the secretory function of the corpora allata, paired glands that synthesize juvenile hormone (Fig. 12-13) in insect larvae [15]. Juvenile hormone is an isoprenoid ester, but the details of its Structure vary from species to species. A specific binding protein protects juvenile hormone from the action of degradative Enzymes. However, in the hawkmoth, from the earliest stages of pupal differentiation, an esterase is produced that hydrolyzes the protein-bound juvenile hormone [16].

The insect prothoracic gland secretes the steroid hormone ecdysone (Fig. 12-18). Also known as the molting hormone, it is essential for the periodic shedding of the larval exoskeleton. It also stimulates molting in crustaceans and other Arthropods. Ecdysone appears to be required by more primitive animal groups as well, specifically schistosomes and nematodes. In addition to α-ecdysone, its hydroxylated derivatives—20-hydroxyecdysone, 26-hydroxyecdysone, and 20,26-dihydroxyecdysone—have been isolated from insects [17]. It has been suggested that different ecdysones may influence various stages of insect development.

Ecdysone stimulates RNA Synthesis in Tissues. This effect has been visually demonstrated using polytene Chromosomes from fly larvae. Within 15 minutes of ecdysone application, a puff (Swelling) appeared at a specific chromosome band; after some time, a second puff emerged while the first began to recede. Thus, much like mammalian Steroid Hormones, ecdysone appears to directly regulate the METABOLISM/31.html">Transcription process.