Which of the following causes vasodilation in the pulmonary circulation?: (A) Hypercarbia, (B) Hypoxia, (C) PGE, (D) PGI
Answer is D. Substances producing pulmonary vasodilation include nitric oxide, prostacyclins, a2 and b2 adrenergic stimulation, histamine etc. Hypercapnia, hypoxy endothelin I, a1 adrenergic, angiotensin II, thromboxane produce pulmonary vasoconstriction.