Lindberg B F, Bengtsson H I, Lundin S, Andersson K E
Department of Clinical Pharmacology, University Hospital of Lund, Sweden.
Regul Pept. 1992 Nov 20;42(1-2):85-96. doi: 10.1016/0167-0115(92)90026-q.
Atrial natriuretic peptide (ANP), a 28-residue peptide with cardiovascular and renal effects, is rapidly cleared from the circulation. Beside renal clearance, an extra-renal metabolism by the enzyme neutral endopeptidase-24.11 (NEP-24.11) has been proposed, since specific NEP-24.11-inhibitors increase endogenous plasma-ANP. NEP-24.11 is present in rat lung but its significance for ANP hydrolysis within the lung is unclear. The aim of this study was to investigate a possible degradation of rat ANP in a membrane preparation from rat lung. Hydrolysis products of ANP were separated by HPLC and further characterized by a pulmonary artery bioassay, by radioimmunoassay with different antisera, by peptide sequencing and by masspectrometry. Rat pulmonary membranes degraded ANP to one main metabolite lacking biological activity and with poor cross-reactivity to an antiserum recognising the central ring-structure of the peptide. Formation of the hydrolysis product was prevented by the NEP-24.11-inhibitor phosphoramidon (1 microM). Peptide sequencing of the metabolite revealed a cleavage between Cys7 and Phe8, which was confirmed by mass-spectrometry. The metabolite had an HPLC elution time identical to that of the product formed by purified porcine NEP-24.11. These findings suggest that ANP is metabolized and inactivated by endopeptidase-24.11 in rat lungs, the first organ exposed to ANP released from the heart.
心房利钠肽（ANP）是一种具有28个氨基酸残基的肽，对心血管和肾脏有作用，可迅速从循环系统中清除。除了肾脏清除外，有人提出该肽可通过中性内肽酶-24.11（NEP-24.11）进行肾外代谢，因为特异性NEP-24.11抑制剂可增加内源性血浆ANP。NEP-24.11存在于大鼠肺中，但其在肺内对ANP水解的意义尚不清楚。本研究的目的是研究大鼠肺膜制剂中大鼠ANP是否可能降解。通过高效液相色谱（HPLC）分离ANP的水解产物，并通过肺动脉生物测定、使用不同抗血清的放射免疫测定、肽测序和质谱进一步表征。大鼠肺膜将ANP降解为一种主要代谢产物，该代谢产物缺乏生物活性，与识别该肽中央环结构的抗血清交叉反应性较差。NEP-24.11抑制剂磷酰胺素（1 microM）可阻止水解产物的形成。代谢产物的肽测序显示在Cys7和Phe8之间有切割，这通过质谱得到证实。该代谢产物的HPLC洗脱时间与纯化的猪NEP-24.11形成的产物相同。这些发现表明，ANP在大鼠肺中被内肽酶-24.11代谢并失活，肺是心脏释放的ANP接触的第一个器官。
