Periportal expression of the serine dehydratase gene in rat liver

Ogawa, Hirofumi; Kawamata, Seiichi

doi:10.1007/bf00179563

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“…enzymes of serine ⁄ glycine metabolism: Glycine decarboxylase, a component of the glycine dehydrogenase complex that converts glycine to serine, is predominantly expressed in periportal cells; the same holds true for the enzymes of serine catabolism, namely serine dehydratase and serine dehydratase-like. This is in agreement with results of previous studies describing periportal localization of serine dehydratase at the mRNA level [20]. Enhanced serine metabolism in periportal hepatocytes may contribute to the availability of substrates for gluconeogenesis, a pathway that is also located mainly in periportal hepatocytes [1].…”

Section: Discussionsupporting

confidence: 93%

Differential gene expression in periportal and perivenous mouse hepatocytes

et al. 2006

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Hepatocytes play a pivotal role in both the synthesis and degradation of numerous endogenous biomolecules, thus maintaining metabolic homeostasis, as well as in the conversion and detoxification of xenobiotic compounds. Based on the location of the blood vessels, the terminal branches of the portal and the hepatic (central) veins and on the direction of the blood flow, hepatocytes of each liver lobule can be divided into two subpopulations, an upstream 'periportal' and a downstream 'perivenous' (pericentral) population. Zonal-specific differences in the metabolic capacities of many enzymes or other proteins, and -to a lesser extent ) of their corresponding messenger RNAs, have been subject to extensive studies throughout the last decades.Many enzymes of intermediary metabolism are not distributed uniformly throughout the liver, but are preferentially expressed in either the periportal or the perivenous hepatocyte subpopulation [1][2][3]. Hence, hepatocytes located in either of the two regions have different, often complementary, functions. Whereas, for example, glycolysis is exclusively active in perivenous hepatocytes, key enzymes of gluconeogenesis, the antagonist pathway, are preferentially expressed in periportal hepatocytes [1]. Zonal-specific expression has also been established for enzymes of amino acid and ammonia metabolism, showing, for example, a higher activity of the urea cycle in periportal cells compared to perivenous hepatocytes [3], whereas glutamine synthesis is exclusively active in the perivenous Hepatocytes located in the periportal and perivenous zones of the liver lobule show remarkable differences in the levels and activities of various enzymes and other proteins. To analyze global gene expression patterns of periportal and perivenous hepatocytes, enriched populations of the two cell types were isolated by combined collagenase ⁄ digitonin perfusion from mouse liver and used for microarray analysis. In total, 198 genes and expressed sequences were identified that demonstrated a ‡ 2-fold difference in expression between hepatocytes from the two different zones of the liver. A subset of 20 genes was additionally analyzed by real-time RT-PCR, validating the results obtained by the microarray analysis. Several of the differentially expressed genes encoded key enzymes of intermediary metabolism, including those involved in glycolysis and gluconeogenesis, fatty acid degradation, cholesterol and bile acid metabolism, amino acid degradation and ammonia utilization. In addition, several enzymes of phase I and phase II of xenobiotic metabolism were differentially expressed in periportal and perivenous hepatocytes. Our results confirm previous findings on metabolic zonation in liver, and extend our knowledge of the regulatory mechanisms at the transcriptional level.Abbreviations GS, glutamine synthetase.

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Section: Discussionsupporting

confidence: 93%