Aldosterone

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Image:Aldosterone-2D-skeletal.png Aldosterone is a steroid hormone (mineralocorticoid family) produced by the outer-section (zona glomerulosa) of the adrenal cortex in the adrenal gland to regulate sodium and potassium balance in the blood. It is synthesized from cholesterol by aldosterone synthase, which is absent in other sections of the adrenal gland. It is the sole endogenous member of the class of mineralocorticoids in human (corticosterone in rodent). Acting on mineralocorticoid receptors (MR) on principal cells in the distal tubule of the kidney nephron, it increases the permeability of their apical (luminal) membrane to potassium and sodium and activates their basolateral Na⁺/K⁺ pumps, stimulating ATP hydrolysis, reabsorbing sodium (Na⁺) ions and water into the blood, and excreting potassium (K⁺) ions into the urine. Aldosterone also stimulates H⁺ secretion by α-intercalated cells in the collecting duct, regulating plasma bicarbonate (HCO3⁻) levels and its acid/base balance.<ref>Brenner & Rector's The Kidney, 7th ed. Saunders, 2004.</ref>

Aldosterone is responsible for the reabsorption of about 2% of filtered sodium in the kidneys, which is nearly equal to the entire sodium content in human blood under normal GFR (glomerular filtration rate).<ref>Sherwood, L. Human Physiology, from Cells to Systems, 4th Ed., Brooks/Cole, 2001</ref>

Unlike neuroreceptors, classic steroid receptors are intracellularly located. The aldosterone/MR receptor complex binds on the DNA to specific hormone response element, which leads to gene specific transcription. Some of the transcribed genes are crucial for transepithelial sodium transport, including the three subunits of the epithelial sodium channel, the Na⁺/K⁺ pumps and their regulatory proteins serum and glucocorticoid-induced kinase, and channel-inducing factor respectively.

Aldosterone synthesis is stimulated by increased plasma angiotensin II, ACTH, or potassium levels, which are present in proportion to plasma sodium deficiencies. It is also stimulated by plasma acidosis. The secretion of aldosterone has a diurnal rhythm.<ref>Hurwitz S, Cohen R, & Williams GH. Diurnal variation of aldosterone and plasma renin activity: timing relation to melatonin and cortisol and consistency after prolonged bed rest. 2004 J Appl Physiol 96: 1406-1414. Full Text</ref>

Aldesterone release is also stimulated by the stretch receptors located in the atria of the heart. If decreased blood pressure is detected, the adrenal gland is stimulated by these stretch receptors to release aldesterone, which increases sodium reabsorption from the urine, sweat and the gut. This causes increased osmolarity in the extracellular fluid which will eventually return blood pressure toward normal.

1 Aldosterone and the kidney
- 1.1 Control of aldosterone release
2 References
3 External links

[edit] Aldosterone and the kidney

[edit] Control of aldosterone release

The role of the renin-angiotensin system
The role of sympathetic nerves
The role of baroreceptors
The role of the juxtaglomerular apparatus
The plasma concentration of potassium

[edit] References

Williams JS, Williams GH. 50th anniversary of aldosterone. J Clin Endocrinol Metab. 2003 Jun;88(6):2364-72. Full text. PMID 12788829.

[edit] External links

Link page to external chemical sources.

Hormones and endocrine glands - edit

Hypothalamus: - TRH - CRH - GnRH - GHRH - somatostatin - dopamine | Posterior pituitary: vasopressin - oxytocin - lipotropin | Anterior pituitary: GH - ACTH - TSH - LH - FSH - prolactin - MSH - endorphins - lipotropin

Stomach: gastrin | Duodenum: CCK - GIP - secretin - motilin - VIP | Ileum: enteroglucagon | Liver: IGF-1

Placenta: hCG - HPL - estrogen - progesterone

Adipose tissue: leptin, adiponectin

Target-derived NGF, BDNF, NT-3

Urinary system - Kidney - edit
Renal capsule \| Renal cortex \| Renal medulla (Renal sinus, Renal pyramids) \| Renal calyx \| Renal pelvis
Nephron - Renal corpuscle (Glomerulus, Bowman's capsule) → Proximal tubule → Loop of Henle → Distal convoluted tubule → Collecting ducts Juxtaglomerular apparatus (Macula densa, Juxtaglomerular cells, Extraglomerular mesangial cells) Renal circulation - Renal artery → Interlobar arteries → Arcuate arteries → Cortical radial arteries → Afferent arterioles → Glomerulus → Efferent arterioles → Vasa recta → Arcuate vein→ Renal vein
Renal physiology
Filtration - Ultrafiltration \| Countercurrent exchange Hormones effecting filtration - Antidiuretic hormone (ADH) \| Aldosterone \| Atrial natriuretic peptide Endocrine - Renin \| Erythropoietin (EPO) \| Calcitriol (Active vitamin D) \| Prostaglandins
Assessing Renal function / Measures of dialysis
Glomerular filtration rate \| Creatinine clearance \| Renal clearance ratio \| Urea reduction ratio \| Kt/V \| Standardized Kt/V \| Hemodialysis product

Corticosteroids - glucocorticoid/receptor and mineralocorticoid/receptor edit (A07EA, C05AA, D07, D10AA, H02, R01AD, R03BA, S01BA, S02B, and S03B)
Alclometasone, Aldosterone, Amcinonide, Beclometasone, Betamethasone, Budesonide, Ciclesonide, Clobetasol, Clobetasone, Clocortolone, Cloprednol, Cortisone, Cortivazol, Deflazacort, Deoxycorticosterone, Desonide, Desoximetasone, Desoxycortone, Dexamethasone, Diflorasone, Diflucortolone, Difluprednate, Fluclorolone, Fludrocortisone, Fludroxycortide, Flumetasone, Flunisolide, Fluocinolone acetonide, Fluocinonide, Fluocortin, Fluocortolone, Fluorometholone, Fluperolone, Fluprednidene, Fluticasone, Formocortal, Halcinonide, Halometasone, Hydrocortisone/cortisol, Hydrocortisone aceponate, Hydrocortisone buteprate, Hydrocortisone butyrate, Loteprednol, Medrysone, Meprednisone, Methylprednisolone, Methylprednisolone aceponate, Mometasone furoate, Paramethasone, Prednicarbate, Prednisone/Prednisolone, Prednylidene, Rimexolone, Tixocortol, Triamcinolone, Ulobetasol