Zhang G L, Wang Y H, Teng H L, Lin Z B
Department of Pharmacology, School of Basic Medical Sciences, Beijing University, Beijing 100083, China.
World J Gastroenterol. 2001 Jun;7(3):331-4. doi: 10.3748/wjg.v7.i3.331.
To study the effects of aminoguanidine (AG) and two L-arginine analogues N(omega)-nitro-L-arginine methyl ester (L-NAME) and N(omega)-nitro-L-arginine (L-NNA) on nitric oxide (NO) production induced by cytokines (TNF-alpha, IL-1 beta, and IFN-gamma) and bacterial lipopolysaccharide (LPS) mixture (CM) in the cultured rat hepatocytes, and examine their mechanisms action.
Rat hepatocytes were incubated with AG, L-NAME, L-NNA, Actinomycin D (ActD) and dexamethasone in a medium containing CM (LPS plus TNF-alpha, IL-1 beta, and IFN-gamma) for 24h. NO production in the cultured supernatant was measured with the Griess reaction. Intracellular cGMP level was detected with radioimmunoassy.
NO production was markedly blocked by AG and L-NAME in a dose-dependent manner under inflammatory stimuli condition triggered by CM in vitro. The rate of the maximum inhibitory effects of L-NAME (38.9%) was less potent than that obtained with AG(53.7%, P < 0.05). There was no significant difference between the inhibitory effects of AG and two L-arginine analogues on intracellular cGMP accumulation in rat cultured hepatocytes. Non-specific NOS expression inhibitor dexamethasone (DEX)and iNOS mRNA transcriptional inhibitor ActD also significantly inhibited CM-induced NO production. AG(0.1 mmol x L(-1)) and ActD (0.2 ng x L(-1)) were equipotent in decreasing NO production induced by inflammatory stimuli in vitro, and both effects were more potent than that induced by non-selectivity NOS activity inhibitor L-NAME (0.1 mmol x L(-1)) under similar stimuli conditions (P<0.01).
AG is a potent selective inhibitor of inducible isoform of NOS,and the mechanism of action may be not only competitive inhibition in the substrate level, but also the gene expression level in rat hepatocytes.
研究氨基胍（AG）以及两种L-精氨酸类似物N（ω）-硝基-L-精氨酸甲酯（L-NAME）和N（ω）-硝基-L-精氨酸（L-NNA）对培养的大鼠肝细胞中由细胞因子（TNF-α、IL-1β和IFN-γ）和细菌脂多糖（LPS）混合物（CM）诱导的一氧化氮（NO）生成的影响，并探讨其作用机制。
将大鼠肝细胞与AG、L-NAME、L-NNA、放线菌素D（ActD）和地塞米松在含有CM（LPS加TNF-α、IL-1β和IFN-γ）的培养基中孵育24小时。用Griess反应测定培养上清液中的NO生成量。用放射免疫分析法检测细胞内cGMP水平。
在体外由CM触发的炎症刺激条件下，AG和L-NAME以剂量依赖性方式显著阻断NO生成。L-NAME的最大抑制作用率（38.9%）低于AG（53.7%，P<0.05）。AG和两种L-精氨酸类似物对大鼠培养肝细胞内cGMP积累的抑制作用无显著差异。非特异性NOS表达抑制剂地塞米松（DEX）和iNOS mRNA转录抑制剂ActD也显著抑制CM诱导的NO生成。AG（0.1 mmol·L⁻¹）和ActD（0.2 ng·L⁻¹）在体外降低炎症刺激诱导的NO生成方面具有同等效力，并且在相似刺激条件下两者作用均比非选择性NOS活性抑制剂L-NAME（0.1 mmol·L⁻¹）更强（P<0.01）。
AG是一种有效的诱导型NOS同工酶选择性抑制剂其作用机制可能不仅是在底物水平的竞争性抑制，还包括在大鼠肝细胞中的基因表达水平。
