Question:hard
An important non-respiratory function of the lungs is:
An important non-respiratory function of the lungs is:
Show Hint
Recall the enzyme on lung endothelium that activates angiotensin II and drives aldosterone.
Updated On: Jun 24, 2026
- Anion balance
- Sodium balance
- Potassium balance
- Calcium balance
Show Solution
The Correct Option is B
Solution and Explanation
This item asks you to look past gas exchange and recall the metabolic side jobs of the lung. The pulmonary vascular bed is a busy biochemical organ: it filters microemboli, stores blood, deactivates serotonin and bradykinin, and most importantly contains angiotensin converting enzyme on its endothelium.
That ACE step is the link to the options. As blood passes through the lung, ACE converts angiotensin I into the active angiotensin II. Angiotensin II then stimulates aldosterone secretion, and aldosterone makes the kidney retain sodium. So the lung sits at the start of the cascade that controls how much sodium the body holds onto, tying the lung to sodium balance.
The other electrolytes do not run through the lung in this way. Potassium is handled mainly by the kidney and by insulin and acid base shifts, calcium is governed by parathyroid hormone, vitamin D, the gut and bone, and the broad anion balance is again a renal and metabolic affair. None of these depends on a pulmonary enzymatic step.
$\Rightarrow$ among the choices, the lung most clearly influences sodium balance through its ACE driven angiotensin and aldosterone pathway.
\[\boxed{\text{Sodium balance}}\]
That ACE step is the link to the options. As blood passes through the lung, ACE converts angiotensin I into the active angiotensin II. Angiotensin II then stimulates aldosterone secretion, and aldosterone makes the kidney retain sodium. So the lung sits at the start of the cascade that controls how much sodium the body holds onto, tying the lung to sodium balance.
The other electrolytes do not run through the lung in this way. Potassium is handled mainly by the kidney and by insulin and acid base shifts, calcium is governed by parathyroid hormone, vitamin D, the gut and bone, and the broad anion balance is again a renal and metabolic affair. None of these depends on a pulmonary enzymatic step.
$\Rightarrow$ among the choices, the lung most clearly influences sodium balance through its ACE driven angiotensin and aldosterone pathway.
\[\boxed{\text{Sodium balance}}\]
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