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Physiology

Endocrine

Question 166 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

Renin-Angiotensin-Aldosterone System. (Image by Mikael Häggström [Public domain], via Wikimedia Commons)

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Close
  • 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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