Substance regulated by ADH's effects on the renal tubules is:
a. Ammonium ions
b. Bicarbonate
c. Calcium
d. Chloride
e. Hydrogen ions
f. Magnesium
g. Phosphate
h. Potassium
i. Sodium
j. Water

Verified step by step guidance

1. Step 1: Understand the role of ADH (antidiuretic hormone) in the body. ADH primarily acts on the kidneys, specifically on the renal tubules, to regulate the reabsorption of water.
2. Step 2: Recall that ADH increases the permeability of the collecting ducts in the kidneys to water, allowing more water to be reabsorbed back into the bloodstream, which concentrates the urine and reduces water loss.
3. Step 3: Review the list of substances provided and consider which one is directly affected by ADH's action on the renal tubules. ADH does not primarily regulate ions like ammonium, bicarbonate, calcium, chloride, hydrogen, magnesium, phosphate, potassium, or sodium.
4. Step 4: Recognize that the main substance regulated by ADH in the renal tubules is water, as ADH controls water reabsorption to maintain body fluid balance and osmolarity.
5. Step 5: Conclude that the correct answer is the substance whose reabsorption is directly influenced by ADH, which is water.

Key Concepts

Antidiuretic Hormone (ADH) Function

ADH, also known as vasopressin, primarily regulates water balance in the body by increasing water reabsorption in the renal tubules. It acts on the collecting ducts of the kidney to make them more permeable to water, reducing urine volume and concentrating the urine.

Renal Tubule Physiology

The renal tubules are structures in the nephron where selective reabsorption and secretion occur. Different segments handle various substances like ions, water, and solutes, with ADH specifically targeting the collecting ducts to control water permeability.

Water Reabsorption Mechanism

Water reabsorption in the kidneys is regulated by ADH through insertion of aquaporin channels in the collecting duct cells. This process allows water to move from the tubular fluid back into the bloodstream, maintaining body fluid balance and preventing dehydration.