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Gillis CN. 
“Metabolism of Vasoactive Hormones by Lung.”. 
Anesthesiology. 1973;39(6):626-632.
The metabolism of vasoactive hormones and drugs (see below) by the lung is reviewed. A wide variety of hormones and drugs are concentrated or metabolized by lung after systemic administration. Whilst many are organic bases, they lack common chemical characteristics, although the lung shows a remarkable degree'of specificity, e.g. norepine - phrine (NE) but not epinephrine is removed from pulmonary blood. 5-Hydroxytryptamine (5HT) is taken up by pulmonary tissue and then deaminated by monoamine oxidase-in animal lungs. 800f 4C-5HT taken up by rat lung was metabolically degraded and the remainder was firmly bound to lung and could be detected up to 1 wk afterwards. 650f 4C-5HT given as a bolus i.v. injection was removed by the lungs of anesthetized patients in 1 study. It has been suggested that derangement of pulmonary uptake of-5HT may be associated with- venous thrombosis since 5HT levels may increase to promote-platelet aggregation. Pulmonary hypertension may in - volve alterations in the uptake of NE and 5HT. Drugs which inhibit the uptake of these amines by lungs may cause abnormally high circulating levels of NE and 5HT. About 20-250f N E infusions are removed by animal and human lungs. The site of uptake of NE is different from that of 5HT and is unrelated to adrenergic innervation. NE uptake sites appear to be the endothelial cells of capillaries and venules. NE uptake is highly temperature dependent. Bradykinin can be 80 0nactivated by pulmonary circulation and this process appears primarily enzymatic. Another vasoactive peptide- angiotensin I is substantially converted to angiotensin II by the lung. Conversion in the blood is too slow to account for the rapid pressor response to angiotensin I. Angiotensin II passes through the lung-without alteration. Conversion probably occurs in the capillary endothelium. Release and synthesis of prostaglandins El and E2 by the lung has been reported. Over 900f infused E1, E2 and F2 is removed by the lungs. However, PGA and Az pass freely. It has been suggested that PGE: may be involved m migraine but substantial proof is lacking at present. The presence of microsomal enzymes in the lungs suggests that they may have metabolizing potential for such compounds as halo - thane.
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