Question

Describe in detail the physiology of aldosterone with respect to potassium balance (just K+, sodium is covered in the next question). Include a detailed description of what aldosterone is, where it comes from, and how its sectretion is regulated. Then describe its physiological effects (just with respect to K+) and explain why they are important.

Answer 1

synthesis of aldosterone

Regulation of aldosterone

Physiological effects

Aldosterone affects the ultimate part of electrolyte and water absorption within the uriniferous tubule before excretion in the urine. As a result, aldosterone solely affects somewhat 3% of the full water absorption and is used in the fine-tuning of absorption. Steroid hormones accomplish this by spreading into principle cells among the late distal tubule and collecting duct, where it acts on the nucleus of the cell to increase ribonucleic acid synthesis. These mRNAs are then used to increase the expression of Na channels, sodium-potassium ATPase, and enzymes of the citric acid cycle.

This creates a concentration gradient which results in reabsorption of sodium (Na+) ions and water (which follows sodium) into the blood, and secreting potassium (K+) ions into the urine (lumen of collecting duct).

Aldosterone upregulates epithelial sodium channels (ENaCs) in the collecting duct and the colon, increasing apical membrane permeability for Na+ and thus absorption.