Rannels D E, Addison J L
Am J Physiol. 1987 Jan;252(1 Pt 1):E96-101. doi: 10.1152/ajpendo.1987.252.1.E96.
Uptake of the polyamine spermidine (SPD) from the pulmonary circulation was characterized by using ventilated rat lungs perfused in situ with Krebs-Henseleit-bicarbonate buffer containing 4.5% bovine serum albumin, 5.6 mM glucose, and 20 amino acids at plasma levels. [14C]SPD was accumulated by the lungs in a time- and concentration-dependent manner. The pathway of SPD uptake exhibited saturation kinetics with an apparent Km in the range of 1 microM and a Vmax of 450-540 pmol/g lung min. SPD uptake was inhibited by the naturally occurring polyamines putrescine and spermine (SPM) and by the inhibitor of polyamine synthesis, methyglyoxal bis(guanylhydrazone) (MGBG). Inhibition of SPD uptake by SPM followed competitive kinetics; although MGBG was also a competitive inhibitor of SPD uptake, MGBG was less effective than SPM. These observations indicate that SPD is taken up from the pulmonary circulation by a carrier-mediated pathway that is inhibited by other natural polyamines and by MGBG and exhibits substrate affinity in the range of plasma SPD concentrations.
通过使用在体灌注的通气大鼠肺来表征肺循环中多胺亚精胺（SPD）的摄取情况，灌注液为含有4.5%牛血清白蛋白、5.6 mM葡萄糖和血浆水平20种氨基酸的Krebs-Henseleit-碳酸氢盐缓冲液。肺以时间和浓度依赖性方式积累[14C]SPD。SPD摄取途径呈现饱和动力学，表观Km在1 microM范围内，Vmax为450 - 540 pmol/g肺·分钟。天然存在的多胺腐胺和精胺（SPM）以及多胺合成抑制剂甲基乙二醛双（脒腙）（MGBG）可抑制SPD摄取。SPM对SPD摄取的抑制遵循竞争性动力学；尽管MGBG也是SPD摄取的竞争性抑制剂，但MGBG的效果不如SPM。这些观察结果表明，SPD通过载体介导的途径从肺循环中摄取，该途径受到其他天然多胺和MGBG的抑制，并且在血浆SPD浓度范围内表现出底物亲和力。
