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Physiology
Endocrine
Question 6 of 180
Aldosterone primarily acts at which of the following sites in the renal nephron:
Answer:
Aldosterone acts mainly at the renal distal convoluted tubule (DCT) to cause sodium retention and potassium loss. It increases the synthesis of transport mechanisms in the distal nephron including the Na+ pump, Na+/H+ antiporter, and Na+ and K+ channels in principal cells, and H+ ATPase in intercalated cells. Na+ (and thus water) reabsorption and K+ and H+ secretion are thereby enhanced.Aldosterone
Physiology / Endocrine / Adrenal Function / Renal / Mechanism of Filtration
Last Updated: 2nd May 2021
Aldosterone is secreted by the zona glomerulosa of the adrenal cortex.
Stimulating Factors
Aldosterone release is stimulated by:
- Angiotensin II (secondary to a fall in blood volume, blood pressure or plasma [Na+])
- High plasma [K+]
- ACTH
N.B. ACTH is less important as a regulator, so pituitary failure does not severely impair aldosterone secretion.
Function
Aldosterone acts mainly at the renal distal convoluted tubule (DCT) to cause sodium retention and potassium loss. It increases the synthesis of transport mechanisms in the distal nephron including the Na+ pump, Na+/H+ antiporter, and Na+ and K+ channels in principal cells, and H+ ATPase in intercalated cells. Na+ (and thus water) reabsorption and K+ and H+ secretion are thereby enhanced.
![By Mikael Häggström (All used images are in public domain.) [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/10/461px-Renin-angiotensin_system_in_man_shadow.svg_.png)
Renin-Angiotensin-Aldosterone System. (Image by Mikael Häggström [Public domain], via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
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