Angiotensin-converting enzyme kinetics in an endothelial cell column.
Angiotensin-converting enzyme kinetics in an endothelial cell column.
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内皮细胞柱中的血管紧张素转换酶动力学。
DOI：
10.1152/ajplung.1990.258.4.l188
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Mueller,SN
中科院分区：
文献类型：
--
作者：
Howell,RE;Haselton,FR;Mueller,SN
The kinetics of saturable endothelial metabolic functions have been assessed in vivo by transient (indicator-dilution) measurements and in culture by steady-state measurements, but comparisons between the two are difficult. Therefore, we used indicator-dilution methods to assess the kinetics of angiotensin-converting enzyme (ACE) activity in cultured endothelium. Bovine fetal aortic endothelial cells were grown to confluence on microcarrier beads. Cell-covered beads were poured into polypropylene columns and perfused with serum-free culture medium. Six injections, containing [3H]benzol-Phe-Ala-Pro [( 3H]BPAP, an ACE substrate) and varying amounts of unlabeled BPAP, were applied to each column and effluent was collected in serial samples. The apparent kinetics of BPAP metabolism were determined by four models used previously to determine pulmonary endothelial ACE kinetics in vivo, the most useful model incorporating transit time heterogeneity. The Km averaged 5 microM, which is close to values determined previously in vivo and in vitro. The Amax (Vmax.reaction volume) and Amax/Km averaged 6 nmol/min and 1.5 ml/min, respectively, which are lower than estimates in vivo. In conclusion, we have developed a new method for investigating saturable metabolic activity in cultured endothelium, which after further exploration should also enable better comparisons of endothelial metabolic functions in vivo and in culture.
