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Hormonal Regulation of Sodium, Potassium, Calcium, and Magnesium Ions
Published in Robert B. Northrop, Endogenous and Exogenous Regulation and Control of Physiological Systems, 2020
A hormone receptor has a high specific affinity for its corresponding hormone molecule. That is, when the hormone molecule encounters its receptor, a strong chemical bond forms between them, locking them together. The binding of a hormone with its receptor triggers a sequence of chemical events which leads to the hormonal effect on the cell. One such biochemical scenario is that the binding activates the enzyme adenyl cyclase in the membrane. The adenyl cyclase molecule exposed to the cytoplasm causes immediate conversion of adenosine triphosphate in the cytoplasm to cyclic adenosine monophosphate (cAMP), which then initiates a number of cellular functions including protein synthesis before adenyl cyclase is inactivated. cAMP is known as a second messenger. The type of cell determines what the end product of cAMP production will be; for example, in a thyroid cell, cAMP triggers the production of thyroid hormone; in a renal tubule epithelial cell, cAMP increases the membrane permeability to water.
Water
Published in Takashiro Akitsu, Environmental Science, 2018
An organ on which a hormone acts is called a target organ, and a cell on which it actually acts is called a target cell. Here, there are hormone receptors, which are proteins that specifically bind to hormone molecules.
Toxicity and Toxins
Published in Gary S. Moore, Kathleen A. Bell, Living with the Earth, 2018
Gary S. Moore, Kathleen A. Bell
Endocrine disruptors have been referred to as xeno-estrogens, estrogenic, hormone-mimicking, and endocrine-disrupting chemicals. The synthetic chemicals presently identified include a number of pesticides such as DDT, lindane, and atrazine plasticizers such as phthalates and alkylphenols; bisphenol A; PCBs; dioxin; the common food antioxidant butylated hydroxyanisol (BHA); and several fungicides. A variety of naturally occurring plant compounds or phytoestrogens are also known to have estrogen compounds (Table 5.2). There are at least four different mechanisms by which endocrine disruptors can exert their adverse effects (Figure 5.17). Some endocrine disrupters are similar enough to the native hormone that they can occupy its site on the receptor tissue causing a cascade of events as if the native hormone had bound to the site. Such a chemical is called a hormone mimic. Some chemicals may bind to the site but are not similar enough to activate a response. They may simply prevent normal hormonal action through a hormone block.Endocrine disruptors may cause artificial and unwelcome changes in the numbers of hormone receptor sites on tissues and organs.An endocrine disruptor may cause a change in the production of a hormone, either increasing its production or decreasing, thereby changing the concentration of the hormone in the body. Small amounts of a change in a hormone can have large effects on the target organ.Endocrine disruptors may replace hormones on the carrier proteins that transport hormones via the blood stream to various parts of the body. This makes some proportion of the population native functional hormone unavailable and produces adverse health consequences that may be barely noticeable to very severe.21Endocrine disruptors were originally labeled as estrogens or androgens based on their ability to bind to estrogen receptors or androgen receptors, respectively. Little thought was given to the possibility of a disruptor being able to bind to both types of receptors. However, recent studies in vitro reveal that some environmental pollutants can bind to estrogenic receptors, androgenic receptors, and binding proteins. If this phenomenon occurs in living organisms, then the effects of environmental disruptors may occur across several different receptor sites and magnify the effects, making even very low concentrations quite potent.36
Impact of occupational cadmium exposure on bone in sewage workers
Published in International Journal of Occupational and Environmental Health, 2018
Mona M Taha, Heba Mahdy-Abdallah, Eman M Shahy, Khadiga S Ibrahim, Safaa Elserougy
Accumulating evidence suggested that estrogen seems to play a major role in male bone metabolism [16]. Estrogen effect was mediated by estrogen receptor (estrogen receptor alpha [ER-α]), which represents a member of steroid hormone receptor family. It functions as an important part of the hormone–receptor complex that promotes specific target genes expression [17]. Genetic alterations in multiple genes can account for this genetic component and ER-α gene represents one of the various potential candidates. Kim et al. [17] recorded that ER-α gene polymorphism is associated with osteoporosis development in Korean vegetarian men. Polymorphism of the ER-α gene found on intron 1 may affect gene expression and/or interindividual susceptibility in the estrogen hormone through its regulatory action in mRNA transcription. Other possibility was due to that this polymorphism might be associated with unidentified polymorphisms that is responsible for the quality or function of the protein encoded by the ER-α gene [18].