Which substance is inactivated in the lungs, leading to a decrease in its activity?

Bradykinins are peptides that have potent vasodilatory effects and play a role in inflammation. In the lungs, bradykinins are metabolized by various enzymes, primarily through the action of angiotensin-converting enzyme (ACE) present in the pulmonary vasculature. This inactivation is significant because it leads to a reduction in their overall biological activity.

When bradykinins are inactivated in the lungs, this biochemical process helps to regulate blood pressure and inflammation in the pulmonary circulation. The lungs serve as an important site for the modulation of various vasoactive substances, which include bradykinins. Understanding the function of bradykinins and their metabolism in the lungs is essential, particularly in the context of conditions like pulmonary hypertension or acute lung injury, where their activity may be altered.

As for the other substances mentioned: angiotensin is primarily known for its role in blood pressure regulation and is also activated rather than inactivated in the lungs; norepinephrine is a neurotransmitter that generally does not undergo significant metabolism in the lungs; and serotonin is primarily inactivated in the liver and other tissues rather than in the lungs specifically. Thus, bradykinins are uniquely characterized by their inactivation in the pulmonary environment, leading