Question

In the 1940's, scientists identified a biological activity that caused slow-onset but very prolonged constriction of smooth muscle like that in the lungs, an activity that was not antagonized by antihistamines. They called the causative agent for this activity "slow-reacting substance." Later the name was modified to "slow-reacting substance of anaphylaxis (SRS-A)." This is so potent and is present in such low concentrations that its chemical structure defied analysis for many years. It is now known to consist of a set of peptides that are coupled to a metabolite of arachidonic acid and are called?

Cytokines
Immunoglobulins
Leukocidins
Leukotrienes
Immunophilins

Answer 1

The substance identified in the 1940s causing sustained smooth muscle constriction not affected by antihistamines is known as leukotrienes. These compounds are involved in inflammatory and allergic responses, such as anaphylaxis, which requires the administration of epinephrine for emergency treatment.

Step-by-step explanation:

In the 1940s, scientists identified a biological activity leading to prolonged constriction of smooth muscle, such as that found in the lungs, which was not responsive to antihistamines and was called "slow-reacting substance" or "slow-reacting substance of anaphylaxis (SRS-A)." Later research revealed that this substance consists of a set of peptides coupled to a metabolite of arachidonic acid known as leukotrienes. These compounds are known for their role in the inflammatory response and are implicated in conditions like asthma, where they can cause significant bronchoconstriction.

Leukotrienes are among the substances released during mast cell degranulation during an allergic reaction or anaphylaxis, a severe allergic reaction that can result in shock and respiratory collapse. Unlike antihistamines, which can address mild allergic symptoms, leukotrienes require different treatment approaches. Substances like epinephrine are used in emergency settings to counteract the effects of anaphylaxis by raising blood pressure and relaxing bronchial smooth muscle. Individuals with severe allergies often keep an epinephrine autoinjector handy for immediate treatment to prevent anaphylactic shock.