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* Also stimulated as part of the [[Renin-Angiotensin-Aldosterone System (RAAS) - Anatomy & Physiology | Renin-Angiotensin-Aldosterone System (RAAS)]]
* Also stimulated as part of the [[Renin-Angiotensin-Aldosterone System (RAAS) - Anatomy & Physiology | Renin-Angiotensin-Aldosterone System (RAAS)]]
==Release==
* Release is stimulated by 3 things
# Corticotropin (ACTH)
# [[Renin-Angiotensin-Aldosterone System (RAAS) - Anatomy & Physiology| Angiotensin 2]]
# K<sup>+</sup>
* Its release is inhibited by Atrial Natiuretic Peptide
* Most increases in the concentration of aldosterone however can be explained by increases in the [[Renin-Angiotensin-Aldosterone System (RAAS) - Anatomy & Physiology| Renin-Angiotensin-Aldosterone System]] and therefore angiotensin 2 and/or by increases in K<sup>+</sup> concentration
* Only in severe fluid loss does ACTH significantly stimulate the release of aldosterone
* ANP is secreted in response to sodium/water loading and therefore inhibits aldosterone secretion
==Action==
==Action==
* Works by altering gene transcription
* Diffuses across the cell membrane - lipophillic (essentially steroidal)
* Of the principal cells of [[Distal Tubule - Anatomy & Physiology| distal tubule]]
* Binds to cytoplasmic receptors
* Works by altering gene transcription and increases synthesis of proteins
** Affects ATP levels
** Affects ATP levels
* Affects sodium entry and transport
* Affects sodium entry and transport
* Increases sodium re-uptake to a small degree in distal convoluted tubule
* Increases number of apical sodium channels, NaCl co-transporters and Na<sup>+</sup>K<sup>+</sup>ATPase
* Increases membrane permeability
* Increases sodium pump activity
* Total quantity of sodium is conserved not the actual plasma concentration
** This is because water follows sodium so the volume is altered according to the amount of sodium
** [[Renin-Angiotensin-Aldosterone System (RAAS) - Anatomy & Physiology| Angiotensin 2]] and aldosterone also affect ECF so only quantity affected not concentration
** ADH and thirst response also work together to dilute the ECF so although there is more NaCl the actual concentration is constant.
===Pottassium===
* In cases of increased K<sup>+</sup>
* Increased sodium pump activity increases the amount of K<sup>+</sup> in cells to reduce plasa K<sup>+</sup>
* Generally not excreted
* However if plasma K<sup>+</sup> is still high aldosterone is stimulated
* Causes pottassium secretion
** Pottassium via apical leak channels in the principal cells
* Very tightly regulated system
** Allows large increase in K<sup>+</sup> to have a miniscule effect on plasma K<sup>+</sup>
===Pottassium and Hydrogen===
===Hydrogen===
** Hydrogen by proton secretory proteins
** Hydrogen by proton secretory proteins