De Jonge W J, Dingemanse M A, de Boer P A, Lamers W H, Moorman A F
Department of Anatomy and Embryology, Academical Medical Center, University of Amsterdam, The Netherlands.
Pediatr Res. 1998 Apr;43(4 Pt 1):442-51. doi: 10.1203/00006450-199804000-00002.
Before weaning, arginine biosynthesis from citrulline most likely takes place in the small intestine rather than in the kidney. We studied the expression of ornithine cycle enzymes in the rat small intestine during perinatal development. The spatiotemporal patterns of expression of ornithine aminotransferase, carbamoylphosphate synthetase, ornithine transcarbamoylase, argininosuccinate synthetase, argininosuccinate lyase, and arginase mRNAs were studied by Northern blot analysis and in situ hybridization. In addition, the expression of carbamoylphosphate synthetase and argininosuccinate synthetase protein was studied by immunohistochemistry. Before birth, the developmentally more mature proximal loops of the intestine expressed the mRNAs at higher concentrations than the more distal loops. After birth, this difference was no longer obvious. The mRNAs of argininosuccinate synthetase and argininosuccinate lyase, the enzymes that metabolize citrulline to arginine, were detectable only in the upper part of the villi, whereas the other mRNAs were concentrated in the crypts. The distribution of argininosuccinate synthetase protein corresponded with that of the mRNA, whereas carbamoylphosphate synthetase protein was present in all enterocytes of the crypts and villi. Hepatic arginase mRNA could not be detected in the enterocytes. The spatial distribution of the respective mRNAs and proteins along the villus axis of the suckling small intestine indicates that the basal enterocytes synthesize citrulline, whereas the enterocytes in the upper half of the villus synthesize arginine.
在断奶前，从瓜氨酸合成精氨酸的过程很可能发生在小肠而非肾脏中。我们研究了围产期发育过程中大鼠小肠中鸟氨酸循环酶的表达情况。通过Northern印迹分析和原位杂交研究了鸟氨酸转氨酶、氨甲酰磷酸合成酶、鸟氨酸转氨甲酰酶、精氨琥珀酸合成酶、精氨琥珀酸裂解酶和精氨酸酶mRNA的时空表达模式。此外，通过免疫组织化学研究了氨甲酰磷酸合成酶和精氨琥珀酸合成酶蛋白的表达。出生前，发育更成熟的小肠近端袢中这些mRNA的表达浓度高于更远端的袢。出生后，这种差异不再明显。将瓜氨酸代谢为精氨酸的精氨琥珀酸合成酶和精氨琥珀酸裂解酶的mRNA仅在绒毛上部可检测到，而其他mRNA则集中在隐窝中。精氨琥珀酸合成酶蛋白的分布与mRNA的分布一致，而氨甲酰磷酸合成酶蛋白存在于隐窝和绒毛的所有肠细胞中。在肠细胞中未检测到肝脏精氨酸酶mRNA。哺乳期小肠绒毛轴上各mRNA和蛋白的空间分布表明，基底肠细胞合成瓜氨酸，而绒毛上半部分的肠细胞合成精氨酸。
