Merker M P, Audi S H, Brantmeier B M, Nithipatikom K, Goldman R S, Roerig D L, Dawson C A
Departments of Anesthesiology, Pharmacology/Toxicology, and Physiology, Medical College of Wisconsin, Milwaukee 53226, USA.
Am J Physiol. 1999 Feb;276(2):L341-50. doi: 10.1152/ajplung.1999.276.2.L341.
To examine the hypothesis that trans isomers of bradykinin and [Gly6]bradykinin are preferentially hydrolyzed by lung peptidases, we studied the fractional inactivation of these peptides in the perfused rat lung using a bioassay after a single-pass bolus injection and high-performance liquid chromatography after lung recirculation. In the bioassay studies, when the peptides passed through the lung, 25.6-fold more bradykinin or 7-fold more [Gly6]bradykinin was required to elicit a contraction equivalent to that produced when the peptides did not pass through the lung. In the recirculation studies, hydrolysis progress curves with rapid and slow phases were observed, with a higher fraction of bradykinin than [Gly6]bradykinin hydrolyzed in the rapid phase. Cyclophilin increased the hydrolysis rate during the slow phase for both peptides. Kinetic analysis indicated that the slowly hydrolyzed peptide fraction, presumably the cis fraction, was 0.13 for bradykinin and 0.43 for [Gly6]bradykinin with cis-trans isomerization rate constants of 0.074 and 0.049 s-1, respectively, consistent with published nuclear magnetic resonance studies.
为检验缓激肽和[甘氨酸6]缓激肽的反式异构体优先被肺肽酶水解这一假说，我们在单次推注注射后采用生物测定法，并在肺再循环后采用高效液相色谱法，研究了这些肽在灌注大鼠肺中的部分失活情况。在生物测定研究中，当肽通过肺时，引发与未通过肺时产生的收缩相当的收缩所需的缓激肽比未通过肺时多25.6倍，[甘氨酸6]缓激肽多7倍。在再循环研究中，观察到具有快速和缓慢阶段的水解进程曲线，快速阶段水解的缓激肽比例高于[甘氨酸6]缓激肽。亲环蛋白增加了两种肽在缓慢阶段的水解速率。动力学分析表明，推测为顺式部分的缓慢水解肽部分，缓激肽为0.13，[甘氨酸6]缓激肽为0.43，顺反异构化速率常数分别为0.074和0.049 s-1，与已发表的核磁共振研究结果一致。
