Newman W H, Zhang L M, McDonald M H, Jollow D J, Castresana M R
Department of Anesthesiology, Mercer University School of Medicine, Macon, Georgia, USA.
Anesth Analg. 1995 Dec;81(6):1229-34. doi: 10.1097/00000539-199512000-00019.
A major hypothesis for the mechanism of tolerance to nitroglycerin (NTG) is that continued use causes a decrease in thiol donors within the vascular smooth muscle cell that are essential for the effect of NTG. We tested this idea directly in the target cell. NTG tolerance, measured as reduced formation of intracellular cyclic guanosine monophosphate (cGMP), was induced in pig coronary smooth muscle cells. The consequence of altering intracellular levels of the thiol donors, glutathione (GSH) and L-cysteine (L-cys), was determined. Incubating cells with 100 microM NTG for 1 h caused an 83% reduction in cGMP formation in response to acute readministration of 200 microM NTG for 2 min but was not associated with a reduction in intracellular GSH or L-cys. This result was not altered when intracellular GSH levels were increased three-fold by including 1 mM GSH in the incubation buffer. Also, recovery from tolerance was not affected by supplementation with GSH. Further, the response of cGMP to NTG was not altered by inhibiting the synthesis of GSH and lowering intracellular levels of GSH by 77%. Similar findings were made with supplemental L-cys or N-acetyl-L-cysteine. These results do not support the hypothesis that tolerance to NTG is the result of a reduction of the thiol donors GSH and L-cys within vascular smooth muscle cells.
关于硝酸甘油（NTG）耐受性机制的一个主要假说是，持续使用会导致血管平滑肌细胞内硫醇供体减少，而这些硫醇供体对NTG的作用至关重要。我们在靶细胞中直接验证了这一观点。在猪冠状动脉平滑肌细胞中诱导出NTG耐受性，以细胞内环磷酸鸟苷（cGMP）生成减少来衡量。测定了改变硫醇供体谷胱甘肽（GSH）和L-半胱氨酸（L-cys）细胞内水平的后果。用100微摩尔/升NTG孵育细胞1小时，导致在急性再次给予200微摩尔/升NTG 2分钟后cGMP生成减少83%，但这与细胞内GSH或L-cys的减少无关。当在孵育缓冲液中加入1毫摩尔/升GSH使细胞内GSH水平增加三倍时，这一结果并未改变。此外，补充GSH对耐受性的恢复没有影响。而且，抑制GSH合成并使细胞内GSH水平降低77%，cGMP对NTG的反应也没有改变。补充L-cys或N-乙酰-L-半胱氨酸时也得到了类似的结果。这些结果不支持NTG耐受性是血管平滑肌细胞内硫醇供体GSH和L-cys减少所致的假说。
