Question

Some patients show profound hypotension after abdominal surgery complicated by bacterial infections that produce endotoxins. Such hypotension is often refractory to treatment with conventional vasoconstrictor drugs. This hypotension may be caused by an overproduction of nitric oxide by the induced form of nitric oxide synthase (NOS). Administration of NOS inhibitors specific to this form might be an appropriate treatment for such patients. Nitric oxide A. is formed spontancously by a reduction of \(\mathrm{NO}_{2}\). B. is synthesized only in macrophages. C. is synthesized from arginine. D. acts as a potent vasoconstrictor. E. has three isoforms.

Short answer

Answer: Nitric oxide is synthesized from arginine.

Step-by-step solution

Fact Check: Is nitric oxide formed spontaneously by a reduction of NO2?

Nitric oxide (NO) is not formed spontaneously by a reduction of NO2. Instead, it is produced enzymatically within cells from the amino acid arginine by nitric oxide synthase (NOS). So, statement A is incorrect.

Fact Check: Is nitric oxide synthesized only in macrophages?

NO is not synthesized only in macrophages. It is synthesized in various cell types, including endothelial cells, neurons, and macrophages. Therefore, statement B is also incorrect.

Fact Check: Is nitric oxide synthesized from arginine?

YES, nitric oxide is synthesized from the amino acid arginine through the action of an enzyme called nitric oxide synthase (NOS). This statement (C) is correct.

Fact Check: Does nitric oxide act as a potent vasoconstrictor?

NO actually acts as a potent vasodilator, which means it expands blood vessels, increasing blood flow, and lowering blood pressure. It does not act as a vasoconstrictor, narrowing blood vessels and increasing blood pressure. Therefore, statement D is incorrect.

Fact Check: Does nitric oxide have three isoforms?

NO itself does not have isoforms; however, nitric oxide synthase (NOS), the enzyme responsible for synthesizing nitric oxide, has three isoforms: neuronal NOS (nNOS or NOS1), inducible NOS (iNOS or NOS2), and endothelial NOS (eNOS or NOS3). So, statement E is incorrect. As we can deduce from the facts checked above, the correct answer is: C. Nitric oxide is synthesized from arginine.