Yu Hong, Yoo Paul K, Aguirre Claudia C, Tsoa Rosemarie W, Kern Rita M, Grody Wayne W, Cederbaum Stephen D, Iyer Ramaswamy K
Mental Retardation Research Center, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1732, USA.
J Histochem Cytochem. 2003 Sep;51(9):1151-60. doi: 10.1177/002215540305100905.
Arginase I (AI), the fifth and final enzyme of the urea cycle, detoxifies ammonia as part of the urea cycle. In previous studies from others, AI was not found in extrahepatic tissues except in primate blood cells, and its roles outside the urea cycle have not been well recognized. In this study we undertook an extensive analysis of arginase expression in postnatal mouse tissues by in situ hybridization (ISH) and RT-PCR. We also compared arginase expression patterns with those of ornithine decarboxylase (ODC) and ornithine aminotransferase (OAT). We found that, outside of liver, AI was expressed in many tissues and cells such as the salivary gland, esophagus, stomach, pancreas, thymus, leukocytes, skin, preputial gland, uterus and sympathetic ganglia. The expression was much wider than that of arginase II, which was highly expressed only in the intestine and kidney. Several co-localization patterns of AI, ODC, and OAT have been found: (a) AI was co-localized with ODC alone in some tissues; (b) AI was co-localized with both OAT and ODC in a few tissues; (c) AI was not co-localized with OAT alone in any of the tissues examined; and (d) AI was not co-localized with either ODC or OAT in some tissues. In contrast, AII was not co-localized with either ODC or OAT alone in any of the tissues studied, and co-localization of AII with ODC and OAT was found only in the small intestine. The co-localization patterns of arginase, ODC, and OAT suggested that AI plays different roles in different tissues. The main roles of AI are regulation of arginine concentration by degrading arginine and production of ornithine for polyamine biosynthesis, but AI may not be the principal enzyme for regulating glutamate biosynthesis in tissues and cells.
精氨酸酶I（AI）是尿素循环的第五种也是最后一种酶，作为尿素循环的一部分，它可解除氨的毒性。在其他研究人员之前的研究中，除了灵长类动物血细胞外，在肝外组织中未发现AI，其在尿素循环之外的作用尚未得到充分认识。在本研究中，我们通过原位杂交（ISH）和逆转录聚合酶链反应（RT-PCR）对出生后小鼠组织中的精氨酸酶表达进行了广泛分析。我们还将精氨酸酶的表达模式与鸟氨酸脱羧酶（ODC）和鸟氨酸转氨酶（OAT）的表达模式进行了比较。我们发现，除肝脏外，AI在许多组织和细胞中表达，如唾液腺、食管、胃、胰腺、胸腺、白细胞、皮肤、包皮腺、子宫和交感神经节。其表达比精氨酸酶II广泛得多，精氨酸酶II仅在肠道和肾脏中高表达。已发现AI、ODC和OAT的几种共定位模式：（a）在某些组织中，AI仅与ODC共定位；（b）在少数组织中，AI与OAT和ODC均共定位；（c）在所检查的任何组织中，AI均不单独与OAT共定位；（d）在某些组织中，AI既不与ODC也不与OAT共定位。相比之下，在任何研究的组织中，AII均不单独与ODC或OAT共定位，且仅在小肠中发现AII与ODC和OAT共定位。精氨酸酶、ODC和OAT的共定位模式表明AI在不同组织中发挥不同作用。AI的主要作用是通过降解精氨酸来调节精氨酸浓度以及为多胺生物合成产生鸟氨酸，但AI可能不是调节组织和细胞中谷氨酸生物合成的主要酶。
