The modes of action of juvenile hormones: some questions we ought to ask
1Department of Biology, York University, Ontario, M3J 1P3, Toronto, Canada. davey@yorku.ca
Abstract:
This paper argues that the current dogma that juvenile hormones are structurally unique and constitute a family of derivatives of farnesoic acid which are produced by the corpus allatum (CA), secreted into the hemolymph, frequently transported by binding proteins, enter cells by diffusion across the cell membrane and there the products of the CA interact in some way with the genome, probably via nuclear receptors of the steroid superfamily, may not be tenable. It does so by examining the following questions. How many JHs are there? Are there other sources of JH in insects? Are there non-farnesoids with JH activity in insects? How does JH get into cells? Is the product of the CA the effective hormone? How many modes of action are there? How many receptors are there?
Related Concept Videos
Hormonal Regulation
Hormonal Regulation
Types of Hormones
Types of Hormones
Steroids and eicosanoids fall under the category of lipid-soluble hormones. Steroids are derived from cholesterol and feature four interconnected carbon rings with variable side chains. Notable examples include estradiol from ovaries and testosterone from testes, exemplifying the critical roles of these lipid-soluble hormones in reproductive physiology. Eicosanoids, derived...
Secondary Messengers in Hormone Action
Many hormones bind to transmembrane G protein-coupled receptors that connect to regulatory G proteins. These G proteins can then activate enzymes such as adenylyl cyclase or phospholipase C. Adenylyl cyclase converts ATP to cAMP, activating...
Target Cell Response to Hormones
Notably, the cellular response can be regulated by altering the number of receptors expressed in the cell. For example, prolonged exposure to elevated hormone levels results in a gradual decline or down-regulation in the number of receptors for that specific hormone on the cell surface. Conversely, in response to low hormone levels, cells may use up-regulation, producing an...


