As for catecholamine metabolism？啥意思？

Various specific enzymes in the lung are responsible for extensive metabolism of PGE2, PGE1 and PGF2a, but PGA2 and PGI2 pass through the lung unchanged. As for catecholamine metabolism, specificity for pulmonary prostaglandin metabolism is in the uptake pathways, rather than with the intracellular enzymes.

肺内多种特异性酶负责大量的PGE₂、PGE₁和PGF_2α代谢，但PGA₂和PGI₂以原型通过肺循环。至于儿茶酚胺代谢，肺前列腺素代谢的特异性在于摄取途径，而非细胞内酶的代谢。

As for catecholamine metabolism, specificity for pulmonary prostaglandin metabolism is in the uptake pathways, rather than with the intracellular enzymes.没看明白，尤其是As for catecholamine metabolism,

这段前面好远的地方有那么一段

Catecholamines and Acetylcholine

Noradrenaline (Norepinephrine)

There is a striking difference in the handling of noradrenaline and adrenaline. Although each catecholamine has a half-life of about 20 seconds in blood, about 30% of noradrenaline is removed in a single pass through the lungs, whereas adrenaline (and isoprenaline and dopamine) is unaffected. Monoamine oxidase and catechol-O-methyl transferase within the endothelial cells will metabolize all amine derivatives with equal efficiency. The specificity of pulmonary endothelium for noradrenaline therefore lies with the cell membrane, which selectively takes up only noradrenaline and 5-hydroxytryptamine (5-HT, serotonin).Extraneuronal uptake of noradrenaline is not confined to the endothelium of the lungs, but uptake by the pulmonary circulation (uptake 1) differs from extraneuronal uptake (uptake 2) in other tissues, which is less specific for noradrenaline.

去甲肾上腺素

去甲肾上腺素和肾上腺素在肺循环中代谢差异显著。血液中儿茶酚胺的半衰期约为20秒，一次肺循环代谢约30%的去甲肾上腺素，而肾上腺素（以及异丙肾上腺素和多巴胺）则不被代谢。肺内皮细胞中的单胺氧化酶和儿茶酚-O-甲基转移酶等效代谢所有胺类衍生物。因此，肺内皮特异性地代谢去甲肾上腺素在于细胞膜，其选择性地只摄取去甲肾上腺素和5-羟色胺（5-HT）。去甲肾上腺素的神经外摄取不局限于肺的内皮，与其他组织 （摄取2）相比，肺循环对去甲肾上腺素的的神经外摄取（摄取1）特异性较低。

5-HT is removed very effectively by the lungs, with up to 98% removed in a single pass. There are considerable similarities to the processing of noradrenaline. HT is taken up by the endothelium, mainly in the capillaries, and is then rapidly metabolized by monoamine oxidase. The halflife of 5-HT in blood is about 1 to 2 min, and pulmonary clearance plays the major role in the prevention of its recirculation.

肺能非常有效地代谢5-羟色胺，一次肺循环的代谢率高达98%。与去甲肾上腺素的代谢过程很相似，5-羟色胺被内皮（主要是毛细血管内皮）摄取，然后被单胺氧化酶迅速代谢。血液中5-羟色胺的半衰期约1~2min，肺代谢可有效防止其再循环。

Histamine, dopamine and adrenaline (epinephrine) are not removed from blood on passing through the pulmonary circulation, in spite of the high concentrations of monoamine oxidase in lung tissue. Their removal from the circulation is limited by the lack of a transport mechanism across the endothelium.

尽管肺组织中有丰富的单胺氧化酶，但由于缺乏跨内皮的转运机制，组胺、多巴胺和肾上腺素等分子在通过肺循环时不会被代谢。

看了前面那段，好像也没啥线索