Home Books Katzung & Trevor's Pharmacology: Examination & Board Review, 12e

Chapter 19: Nitric Oxide, Donors, & Inhibitors

Which one of the following is not a nitric oxide donor but causes it to be synthesized and released from endogenous precursors, resulting in vasodilation?

(A) Acetylcholine

(B) Arginine

(C) Isosorbide mononitrate

(D) Nitroglycerin

(E) Nitroprusside

Nitroprusside and organic nitrites (eg, amyl nitrite) and nitrates (eg, nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate) contain NO groups that can be released as NO. Arginine is the normal source of endogenous NO. Acetylcholine, acting on M₃ receptors, stimulates the synthesis of NO from arginine. The answer is A.

An NO-containing molecule that releases nitric oxide in the blood is

(A) Citrulline

(B) Histamine

(C) Isoproterenol

(D) Nitroglycerin

(E) Nitroprusside

Nitroprusside is the only molecule in this list that spontaneously releases NO in the bloodstream. The answer is E.

The inducible isoform of nitric oxide synthase (iNOS, isoform 2) is found primarily in which of the following?

(A) Adipose tissue

(B) Eosinophils

(C) Macrophages

(D) Platelets

(E) Vascular endothelial cells

The inducible form of NOS is associated with inflammation, and the enzyme is found in highest concentration in macrophages, cells that are particularly involved in inflammation. The answer is C.

The primary endogenous substrate for the enzyme nitric oxide synthase (NOS) is

(A) Acetylcholine

(B) Angiotensinogen

(C) Arginine

(D) Citrulline

(E) Heme

Arginine is the substrate and citrulline and NO are the products of NOS acting on arginine. The answer is C.

Which of the following is a recognized effect of nitric oxide (NO)?

(A) Arrhythmia

(B) Bronchoconstriction

(C) Constipation

(D) Inhibition of acute graft rejection

(E) Pulmonary vasodilation

NO does not cause arrhythmias or constipation. It causes bronchodilation and may hasten graft rejection. NO does cause pulmonary vasodilation. The answer is E.

Which of the following is an endogenous inhibitor/inactivator of nitric oxide?

(A) Arginine

(B) Angiotensinogen

(C) Arachidonic acid

(D) Hemoglobin

(E) Thromboxane

Heme and hemoglobin inactivate NO. The answer is D.

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Chapter 19: Nitric Oxide, Donors, & Inhibitors

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Chapter 19: Nitric Oxide, Donors, & Inhibitors

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