Field workers exposed to a plant toxin develop painful fluid-filled blisters. Analysis of the blister fluid reveals high concentrations of a peptide. Which of the following is a peptide that causes increased capillary permeability and edema?
Histamine and bradykinin both cause a marked increase in capillary permeability that is often associated with edema, but histamine is not a peptide. The answer is B.
In a laboratory study of several peptides, one is found that decreases peripheral resistance but constricts veins. Which of the following causes arteriolar vasodilation and venoconstriction?
(A) Atrial natriuretic peptide (ANP)
(E) Vasoactive intestinal peptide
Substance P is a potent arterial vasodilator and venoconstrictor. The answer is D
Which of the following endogenous molecules is elevated in heart failure and when given as a drug is a vasodilator with significant renal toxicity?
(E) Vasoactive intestinal peptide
BNP is an atrial and brain peptide found in increased amounts in patients with heart failure. The commercial formulation (nesiritide) is approved for use in severe acute heart failure but has significant renal toxicity. The answer is C.
A 50-year-old factory worker presents with cardio-respiratory symptoms and careful workup reveals idiopathic pulmonary hypertension. Which of the following binds endothelin receptors and is approved for use in pulmonary hypertension?
Aliskiren, a renin inhibitor, is used in primary hypertension. Capsaicin, the “hot” constituent of hot peppers, is the molecule responsible for release of substance P. Conivaptan, an AVP antagonist, is used in hyponatremia. Sacubitril, a neprilysin antagonist, is used in heart failure. Macitentan, an endothelin antagonist, is used in pulmonary hypertension. The answer is D.
A 60-year-old financial consultant presents with severe pain in a neuronal dermatome region of her chest. This area was previously affected by a herpes zoster rash. Which of the following might be of benefit in controlling this post-herpetic pain?
Substance P is an important pain-mediating neurotransmitter peptide and appears to be involved in post-herpetic pain as well as arthritic pain. Capsaicin can be used topically to deplete substance P stores from sensory nerves. The answer is D.
In a phase 2 clinical trial in hypertensive patients, an endogenous octapeptide vasoconstrictor was found to increase in the blood of patients treated with large doses of diuretics. Which of the following is the most likely endogenous peptide?
(C) Atrial natriuretic peptide
(E) Calcitonin gene-related peptide
(I) Vasoactive intestinal peptide (VIP)
Angiotensin II, an octapeptide, increases when blood volume decreases (a diuretic effect) because the compensatory response causes an increase in renin secretion. Its precursor, angiotensin I, would also increase, but it is a decapeptide. The answer is B.
Which of the following is a vasodilator that increases in the blood or tissues of patients treated with captopril?
(C) Brain natriuretic peptide
(D) Calcitonin gene-related peptide
Bradykinin increases because the enzyme inhibited by captopril, angiotensin converting enzyme, degrades kinins in addition to synthesizing angiotensin II (see Figure 11–3). The answer is B.
Figure 11–3. Actions of aliskiren, angiotensin-converting enzyme inhibitors, and AT1 receptor blockers. Renin converts angiotensinogen to angiotensin I. Block by aliskiren blocks the sequence at its start. ACE is responsible for activating angiotensin I to angiotensin II and for inactivating bradykinin, a vasodilator normally present in very low concentrations. Block of this enzyme thus decreases the concentration of a vasoconstrictor and increases the concentration of a vasodilator. The AT1 receptor antagonists lack the effect on bradykinin levels, which may explain the lower incidence of cough observed with these agents.
Which of the following is an antagonist at NK1 receptors and is used to prevent or reduce chemotherapy-induced nausea and vomiting?
(E) Brain natriuretic peptide
Aprepitant and ondansetron are both used to reduce or prevent chemotherapy-induced nausea and vomiting. Ondansetron is an antagonist at 5-HT3 receptors. The answer is B.