renal sodium ion absorption

Definition

Target type: biologicalprocess

A renal system process in which sodium ions are taken up from the collecting ducts and proximal and distal loops of the nephron. In non-mammalian species, absorption may occur in related structures. [GOC:dph, GOC:mah]

Renal sodium ion absorption is a complex process crucial for maintaining fluid and electrolyte balance in the body. It occurs primarily in the proximal tubule, loop of Henle, and distal convoluted tubule of the nephron. Here's a detailed description:

1. **Proximal Tubule:**
* The majority (65%) of filtered sodium is reabsorbed here.
* Sodium co-transports with glucose, amino acids, and other solutes via apical membrane transporters like the sodium-glucose cotransporter 2 (SGLT2).
* This reabsorption is driven by the electrochemical gradient created by the Na+/K+ ATPase pump located on the basolateral membrane.
* This pump actively transports sodium out of the cell, maintaining a low intracellular sodium concentration.

2. **Loop of Henle:**
* This region plays a key role in concentrating urine.
* The descending limb is permeable to water but relatively impermeable to sodium, allowing water to move out passively.
* The ascending limb is impermeable to water but highly permeable to sodium.
* Sodium is reabsorbed here via the sodium-potassium-2 chloride cotransporter (NKCC2).

3. **Distal Convoluted Tubule:**
* This region fine-tunes sodium reabsorption under hormonal control.
* Sodium reabsorption is regulated by aldosterone, a hormone secreted by the adrenal glands.
* Aldosterone increases the expression of the epithelial sodium channel (ENaC) on the apical membrane, facilitating sodium entry into the cell.

4. **Collecting Duct:**
* Further regulation of sodium reabsorption occurs in the collecting duct.
* Antidiuretic hormone (ADH) promotes water reabsorption in this segment, indirectly influencing sodium concentration.

5. **Regulation of Renal Sodium Absorption:**
* **Hormonal:** Aldosterone, ADH, and atrial natriuretic peptide (ANP) play crucial roles in regulating sodium reabsorption.
* **Physiological:** Changes in blood pressure, blood volume, and plasma sodium concentration influence sodium reabsorption.
* **Dietary:** Sodium intake influences renal sodium excretion, with increased intake leading to increased excretion.

6. **Clinical Implications:**
* Disruptions in renal sodium reabsorption can lead to various conditions, including:
* **Hypernatremia:** High blood sodium levels, potentially due to dehydration.
* **Hyponatremia:** Low blood sodium levels, often due to fluid overload.
* **Hypertension:** High blood pressure due to increased sodium retention.
* **Edema:** Swelling due to fluid retention caused by impaired sodium reabsorption.'
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Proteins (6)

Compounds (168)