Hormonal regulation of glutathione efflux.
Hormonal regulation of glutathione efflux.
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DOI：
10.1016/s0021-9258(17)46192-8
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发表时间：
1990-09
期刊：
影响因子：
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通讯作者：
S. Lu;C. Garcia-Ruiz;J. Kuhlenkamp;M. Ookhtens;M. Salas-Prato;N. Kaplowitz
中科院分区：
文献类型：
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作者：
S. Lu;C. Garcia-Ruiz;J. Kuhlenkamp;M. Ookhtens;M. Salas-Prato;N. Kaplowitz
GSH的外排在离体大鼠肝细胞和灌流肝脏中均表现为可饱和的过程，表明其为载体介导的转运机制。最近的报告提出了激素调节这一过程的可能性。我们目前的工作研究的作用，激素已知影响细胞内信号转导机制的GSH流出培养的大鼠肝细胞和灌注大鼠肝脏。我们发现cAMP依赖性因子，如霍乱毒素（CT）、二丁酰cAMP、毛喉素和胰高血糖素都刺激培养的大鼠肝细胞中的GSH流出。外排动力学进行了比较，在培养的细胞与或不与CT的刺激GSH外排是有关的Vmax的近一倍，而表现出没有显着改变的Km。与这种刺激作用的阈值相关的细胞内cAMP水平的增加比对照高25%。环磷酰胺预处理不能阻断CT的刺激作用，秋水仙碱处理也不能逆转CT的刺激作用。在哇巴因的存在下，胰高血糖素的刺激作用被废除，但在钡的存在下，没有。另一方面，通过Ca ~（2+）和蛋白激酶C起作用的激素，如苯肾上腺素和加压素，对培养细胞中的GSH流出没有影响。在灌注的肝脏模型中，胰高血糖素（10 nM）和双丁酰cAMP（8 μ M）分别刺激肝窦GSH流出至对照值的130和144%，并增加胆汁流量，同时不影响胆汁GSH流出。最后，通过体内胰高血糖素输注后血浆GSH和葡萄糖水平评估胰高血糖素介导的刺激窦状隙GSH流出的生理意义。胰高血糖素显著增加血浆GSH的阈值剂量（5.21 pmol/min）低于葡萄糖（15.61 pmol/min）。在最高胰高血糖素输注速率（261 pmol/min）下，血浆GSH水平加倍，而葡萄糖水平增加80%。总之，增加cAMP刺激GSH流出培养的大鼠肝细胞和灌注的肝脏。cAMP的刺激作用在正弦极发挥，似乎是通过Na（+）-K（+）-ATP酶刺激肝细胞超极化介导的。体内研究证实了cAMP介导的刺激窦状隙GSH流出的重要性，因为它导致血浆GSH水平显著升高。
The efflux of GSH has been shown previously to be a saturable process in both isolated rat hepatocytes and perfused liver, suggesting a carrier-mediated transport mechanism. The possibility in hormonal regulation of this process has been raised by recent reports. Our present work examined the role of hormones known to affect intracellular signal transduction mechanisms on GSH efflux in cultured rat hepatocytes and perfused rat livers. We found that cAMP-dependent factors, such as cholera toxin (CT), dibutyryl cAMP, forskolin, and glucagon all stimulated GSH efflux in cultured rat hepatocytes. The efflux kinetics were compared in cultured cells incubated with or without CT; the stimulation of GSH efflux was related to a near doubling of the Vmax while exhibiting no significant alteration of the Km. The increase in intracellular cAMP level associated with the threshold for this stimulatory effect was 25% above control. The stimulatory effect of CT could not be blocked by cyclohexamide pretreatment or reversed by colchicine treatment. The stimulatory effect of glucagon was abolished in the presence of ouabain but not in the presence of barium. On the other hand, hormones which act through Ca2+ and protein kinase C, such as phenylephrine and vasopressin, had no effect on GSH efflux in the cultured cells. In the perfused liver model, glucagon (10 nM) and dibutyryl cAMP (8 microM) stimulated sinusoidal GSH efflux to 130 and 144% of control values, respectively, and increased bile flow while not affecting biliary GSH efflux. Finally, the physiological significance of glucagon-mediated stimulation of sinusoidal GSH efflux was assessed by both plasma GSH and glucose levels in response to in vivo glucagon infusion. The threshold dose of glucagon for significant increase in plasma GSH (5.21 pmol/min) was lower than for glucose (15.61 pmol/min). At the highest glucagon infusion rate (261 pmol/min), plasma GSH level doubled while glucose level increased 80%. In conclusion, increased cAMP stimulates GSH efflux in cultured rat hepatocytes and perfused livers. The stimulatory effect of cAMP is exerted at the sinusoidal pole and appears to be mediated by hyperpolarization of hepatocytes by stimulation of Na(+)-K(+)-ATPase. In vivo studies confirmed the importance of cAMP-mediated stimulation of sinusoidal GSH efflux as it resulted in significant elevation of the plasma GSH level.