A pharmaceutical company is developing a drug that blocks the DAG arm of the IP3/DAG signaling pathway. Which hormone's action would be MOST affected in vascular smooth muscle?

• A Epinephrine acting on beta-2 receptors
• B Angiotensin II acting on AT1 receptors ✓
• C Glucagon acting on glucagon receptors
• D Insulin acting on its receptor tyrosine kinase

Explanation

Angiotensin II acts via AT1 receptors (Gq-linked GPCR) to activate phospholipase C-beta, generating IP3 (inositol triphosphate) and DAG (diacylglycerol) from PIP2. IP3 releases Ca2+ from sarcoplasmic reticulum; DAG activates protein kinase C (PKC), which together mediate vasoconstriction. Epinephrine on beta-2 receptors uses Gs/cAMP pathway; glucagon uses Gs/cAMP; insulin uses receptor tyrosine kinase — none involve DAG as primary second messenger.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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