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The outermost layer, the zona glomerulosa is the main site for the production of aldosterone, a mineralocorticoid. The synthesis and secretion of aldosterone are mainly regulated by the renin–angiotensin–aldosterone system. The zona glomerulosa cells express a specific enzyme aldosterone synthase (also known as CYP11B2).
Aldosterone upregulates epithelial sodium channels in the collecting duct and the colon, increasing apical membrane permeability for Na + and thus absorption. Cl − is reabsorbed in conjunction with sodium cations to maintain the system's electrochemical balance. Aldosterone stimulates the secretion of K + into the tubular lumen. [17]
In the adrenal glands, it is likely involved in the paracrine regulation of aldosterone secretion; in the heart and vasculature, it may be involved in remodeling or vascular tone; and in the brain, where it is largely independent of the circulatory RAS, it may be involved in local blood pressure regulation.
The production of aldosterone is regulated via the renin-angiotensin II-aldosterone system, a system composed of baroreceptors and juxtaglomerular cells. [ 7 ] [ 8 ] Changes in the homeostasis of the human body, such as osmolality are detected by the system, which causes a chain reaction that ends with the adrenal gland either increasing or ...
The HPA axis also interacts with the immune system through increased secretion of ACTH at the presence of certain molecules of the inflammatory response. [4] Mineralocorticoid secretion is regulated mainly by the renin–angiotensin–aldosterone system (RAAS), the concentration of potassium, and to a lesser extent the concentration of ACTH. [4]
The opposite mechanism is called transrepression. The hormone receptor without ligand binding interacts with heat shock proteins and prevents the transcription of targeted genes. Aldosterone and cortisol (a glucosteroid ) have similar affinity for the mineralocorticoid receptor; however, glucocorticoids circulate at roughly 100 times the level ...
Schematic of the HPA axis (CRH, corticotropin-releasing hormone; ACTH, adrenocorticotropic hormone) Hypothalamus, pituitary gland, and adrenal cortex The hypothalamic–pituitary–adrenal axis (HPA axis or HTPA axis) is a complex set of direct influences and feedback interactions among three components: the hypothalamus (a part of the brain located below the thalamus), the pituitary gland (a ...
In response to stress, the brain directly innervates the thyroid and pancreas for energy regulation, sends signals to the cardiovascular system to increase cardiac output, stimulates the adrenal glands to release cortisol and aldosterone, and releases hormones from the pituitary gland such as ACTH to regulate urine output through the renin ...