Latasa M U, Carretero M V, García-Trevijano E R, Torres L, Mato J M, Avila M A
Unidad de Hepatologia y Terapia Génica, Departamento de Medicina Interna, Facultad de Medicina, Universidad de Navarra, Pamplona, Spain.
J Hepatol. 2000 Nov;33(5):709-15. doi: 10.1016/s0168-8278(00)80300-1.
BACKGROUND/AIMS: The differential oxygenation of periportal and perivenous hepatocytes has been demonstrated as a major determinant in the zonated expression of certain metabolic pathways in the liver. We have searched for novel genes whose expression could be modulated by hypoxia in cultured rat hepatocytes.
Primary cultures of rat hepatocytes were incubated under normoxic (21% oxygen) or hypoxic (3% oxygen) conditions for 6 h. Differences in gene expression under both conditions were analyzed using the technique of differential display by means of PCR.
We have identified the enzyme argininosuccinate lyase (ASL) as being downregulated by hypoxia. ASL is a cytosolic protein which participates in urea metabolism. ASL expression was time-dependently reduced in hypoxia. Hypoxia modulated the responses of this gene to the two main hormonal signals which induce ASL mRNA: glucocorticoids and cAMP. ASL mRNA levels decreased in response to ATP-reducing agents. CoCl2 mimicked the effect of hypoxia, suggesting the implication of a hemoprotein in this response. Hypoxia did not affect ASL mRNA stability, indicating that this effect occurs at the transcriptional level.
Our observations suggest that differences in oxygen levels across the hepatic parenchyma could participate in the zonated expression of ASL.
背景/目的：肝门周和肝静脉周肝细胞的氧合差异已被证明是肝脏中某些代谢途径区域化表达的主要决定因素。我们已寻找在培养的大鼠肝细胞中其表达可被缺氧调节的新基因。
将原代培养的大鼠肝细胞在常氧（21%氧气）或缺氧（3%氧气）条件下孵育6小时。使用PCR差异显示技术分析两种条件下的基因表达差异。
我们已确定精氨酸琥珀酸裂解酶（ASL）这种酶在缺氧时表达下调。ASL是一种参与尿素代谢的胞质蛋白。在缺氧条件下，ASL表达呈时间依赖性降低。缺氧调节了该基因对诱导ASL mRNA的两种主要激素信号的反应：糖皮质激素和cAMP。ASL mRNA水平因ATP降低剂而下降。CoCl2模拟了缺氧的作用，表明血红蛋白参与了这一反应。缺氧不影响ASL mRNA的稳定性，表明这种作用发生在转录水平。
我们的观察结果表明，肝实质内氧水平的差异可能参与了ASL的区域化表达。
