Matsumura Y, Tsukahara Y, Kojima T, Murata S, Murakami A, Takada K, Takaoka M, Morimoto S
Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Japan.
Biol Pharm Bull. 1995 Mar;18(3):401-6. doi: 10.1248/bpb.18.401.
Using cultured human aortic endothelial cells, we examined the effects of phosphoramidon, an endothelin converting enzyme (ECE) inhibitor, on the release of endogenous endothelin-1 (ET-1) and big endothelin-1 (big ET-1), and on the generation of ET-1 from exogenously applied big ET-1. Phosphoramidon, at concentrations of 10(-6) to 2 x 10(-4) M, caused a biphasic alteration of the ET-1 release, i.e., at lower concentrations of the drug, there were slight but unexpected increases of the release, whereas higher concentrations led to a decrease which is due to the drug-induced inhibition of ECE. The former effect appears to be based on the inhibition of ET-1 degradation by neutral endopeptidase 24.11 (NEP), since kelatorphan, a specific NEP inhibitor, produced a similar increasing effect on ET-1 release. Phosphoramidon enhanced the big ET-1 release from the cells in a concentration-dependent manner. When high concentrations of phosphoramidon were added, there was a dramatic increase in the release of big ET-1, which cannot be explained only by the drug-induced inhibition of ECE. This increase in big ET-1 release appeared to be partly due to a transient stimulation of the expression of prepro ET-1 mRNA. The amount of ET-1 generated from exogenously applied big ET-1 was markedly decreased by phosphoramidon in a concentration-dependent manner. In a similar fashion, phosphoramidon markedly inhibited ECE activity of the membrane fraction of cultured cells. Thus, ET-1 generation from exogenously applied big ET-1 reflects the functional phosphoramidon-sensitive ECE activities in human aortic endothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
利用培养的人主动脉内皮细胞，我们研究了内皮素转换酶（ECE）抑制剂磷酰胺素对内源性内皮素-1（ET-1）和大内皮素-1（big ET-1）释放的影响，以及对外源性应用的big ET-1生成ET-1的影响。浓度为10^(-6)至2×10^(-4)M的磷酰胺素引起ET-1释放的双相变化，即药物浓度较低时，释放量有轻微但意外的增加，而较高浓度则导致减少，这是由于药物诱导的ECE抑制作用。前一种效应似乎是基于中性内肽酶24.11（NEP）对ET-1降解的抑制，因为特异性NEP抑制剂凯托芬对ET-1释放产生了类似的增加作用。磷酰胺素以浓度依赖的方式增强了细胞中big ET-1的释放。当加入高浓度的磷酰胺素时，big ET-1的释放急剧增加，这不能仅用药物诱导的ECE抑制来解释。big ET-1释放的这种增加似乎部分是由于前内皮素原-1 mRNA表达的短暂刺激。外源性应用的big ET-1生成的ET-1量被磷酰胺素以浓度依赖的方式显著降低。以类似的方式，磷酰胺素显著抑制了培养细胞膜部分的ECE活性。因此，外源性应用的big ET-1生成ET-1反映了人主动脉内皮细胞中对磷酰胺素敏感的功能性ECE活性。（摘要截断于250字）
