Hormones interaction with

Like steroid hormones, thyroid hormones interact with receptors to alter genomic activity and affect the synthesis of specific proteins during development [25-28], As with testosterone and progesterone, metabolic transformation of thyroxine (T4) is critical to its action [25-28]. Moreover, as with steroid hormones, thyroid hormones alter brain functions in adult life in ways that both resemble and differ from their action during development [25-28]. 

Developmentally, thyroid hormones interact with sex hormones such that hypothyroidism prolongs the critical period for testosterone-induced defeminization (see below) [3] in contrast, the hyperthyroid state prematurely terminates the sensitivity to testosterone [3]. Undoubtedly, an important link in these and other effects is synapse formation. Hypothyroidism increases synaptic density, at least transiently [3]. Interesting parallels with synapse formation are reported for learning behavior in rats neonatal hypothyroidism impairs learning ability, whereas hyperthyroidism accelerates learning initially, followed by a decline later in life [3]. 

The hormone interacts with its receptor by equilibrium binding. The dissociation constant is kJh. 

With the help of co-immimoprecipitation it could be shown that the receptors of steroid hormones interact with at least three chaperones, Hsp90, Hsp70 and Hsp56 (fig. 4.10). The term Hsp (Heat shock protein) is derived from the observation that these proteins were produced at higher levels following heat treatment. Furthermore, one finds a 23 kDa acidic protein in the apo-receptor complex whose fimction is not yet clear. 

Farach-Carson MC, Davis PJ. Steroid hormone interactions with target cells cross talk between membrane and nuclear pathways. J Pharmacol Exp Ther. 2003 307 839-845. 

When a hormone interacts with its receptor, the Gs protein is induced to bind GTP and to dissociate into the G -GTP and G T subunits. The former stimulates adenylate cyclase activity. 

When hepatocytes are exposed to a low concentration of glucagon (1012 M), the hormone interacts with one class of receptors linked to phospholipase C and the hydrolysis of PIP2 [26]. These events lead to an increase in Insl,4,5P3, and presumably to both a mobilization of intracellular Ca2+ and an increase in Ca2+ influx rate. Hence, low concentrations of glucagon act exclusively via the PI system. 

Hormones interact with receptors that are located either inside the cell or within the cell membrane. 

Molecular pharmacology The study of how medication and hormones interact with cells... 

Thyroxine and catecholamine are examples of hormones that are derived from amino acids they are water soluble and circulate in plasma either bound to proteins (thyroxine) or free (catecholamines). Thyroxine binds avidly to three binding proteins and has a half-life of about 7 to 10 days, and the free and unbound catecholamines such as epinephrine have a very short half-life of a minute or less. As do the water-soluble peptide and protein hormones, these hormones interact with membrane-associated receptors and use a second messenger system. 

Let us first look at what happens when one of the body s own messengers (neurotransmitters or hormones) interacts with its receptor. 

Most hormones interacting with intracellular receptors exert their effects by controlling rates of transcription of specific genes. In this case, the hormone binds to a receptor and the complex migrates to the nucleus, where it interacts with specific DNA sites. Hormones in this class include steroids, thyroid hormones (see here), and the hormonal forms of vitamin D. In addition, retinoids, derived from retinoic acid (related to vitamin A), exert regulatory effects in embryonic development through interactions with intracellular receptors. 

W3. Wilber, J. F., and Seibel, M. J., Thyrotropin-releasing hormone interactions with an anterior pituitary membrane receptor. Endocrinology 92, 888-893... 

Hormones are supposed to act only on specific tissues or cells which are called target tissues or target cells. The specificity of hormonal action is expressed at two levels (1) hormone-tissue interaction, and (2) cell reaction to hormonal stimulus. In the target cells, the hormones interact with specific structures— the receptors. The degree of specificity of the receptors conditions the specificity of the interaction. As the receptor for lipolytic hormones in the fat cell reacts with several hormones, so does the fat cell. All cells containing /7-receptors for adrenaline will respond to this hormone. The reaction of a tissue to a hormonal stimulus depends on the metabolic and structural characteristics of this tissue. Thyrotropin activates lipo-lysis in the fat cell, thyroxine synthesis in the thyroid, and insulin secretion by the pancreatic /7-celL... 

It is often postulated that hormones interact with one single species of receptors in the target tissue. All effects of the hormone on the tissue would be more or less distant consequences of this primary interaction (Fig. 1). This is the theory of the unique primary effect of hormones alternative models can be proposed. 

Steroids are a class of lipids characterized by a sterane core and additional functional groups. Hundreds of distinct steroids are found in plants, animals, and fungi. It is possible to classify steroids based on their chemical composition into cholestanes (e.g., cholesterol), cholanes (e.g., cholic acid), pregnanes (e.g., progesterone), and androstanes (e.g., testosterone and androgen). Steroids play many important biological roles, often as hormones interacting with specific receptors. The hydrophobic... 

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