Leukotriene B4 (LTB4), produced from leukotriene A4 by leukotriene A4 hydrolase, is distinguished from the cysteinyl leukotrienes by its principal biological action, which is:

• A Bronchoconstriction and increased vascular permeability
• B Vasodilation of renal afferent arterioles
• C Inhibition of gastric acid secretion
• D Chemotaxis and activation of neutrophils ✓

Explanation

LTB4 acts mainly on BLT receptors on neutrophils, mediating chemotaxis, adhesion, and degranulation, making it central to acute inflammatory recruitment. The cysteinyl leukotrienes LTC4, LTD4, and LTE4 account for slow-reacting substance of anaphylaxis effects such as bronchoconstriction and edema, which kills option A. Gastric mucosal protection belongs to prostaglandins of the E series, and renal vasodilation to PGE2 and PGI2.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

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