Kalra Seema, Seetharam Shakuntla, Yammani Raghunatha R, Seetharam Bellur
VA Medical Center, Research 151, 5000 West National Avenue, Milwaukee, WI 53295, USA.
J Physiol. 2004 Apr 15;556(Pt 2):623-35. doi: 10.1113/jphysiol.2003.058727. Epub 2004 Jan 14.
Transcobalamin (TC) has been cloned and used for studying its gene expression in the rat. TC mRNA is distributed widely in adult rat tissues, but at different levels (kidney > liver > lung > yolk sac > intestine > heart > brain > spleen > muscle). TC mRNA levels were 4-fold higher in the jejunum and ileum compared to its levels in the duodenum. During postnatal development, TC mRNA levels in the ileum declined 4-fold from day 4 to day 12, but increased by 5-fold between days 12 and 24. In contrast, TC mRNA levels increased by 2.5-fold in the kidney from day 4 to day 12 and then declined by 2-fold by day 24. Adrenalectomy of adult rats resulted in a 4-fold decline in ileal levels of TC mRNA and a 50% decline in the ileal mucosal formation of the TC-[(57)Co] cobalamin (Cbl) complex following oral administration of [(57)Co]Cbl complexed to gastric intrinsic factor (IF). Cortisone treatment reversed these changes noted in the ileum. In contrast to ileum, kidney TC mRNA levels were not altered significantly in adrenalectomized rats before and after cortisone treatment. Taken together, this study has provided evidence for the regulation of TC gene expression in the rat kidney and intestine during their postnatal development, and cortisone selectively regulates ileal but not kidney TC mRNA levels.
转钴胺素（TC）已被克隆，并用于研究其在大鼠中的基因表达。TC mRNA广泛分布于成年大鼠组织中，但水平不同（肾脏>肝脏>肺>卵黄囊>肠道>心脏>大脑>脾脏>肌肉）。空肠和回肠中的TC mRNA水平比十二指肠中的高4倍。在出生后发育过程中，回肠中的TC mRNA水平在第4天到第12天下降了4倍，但在第12天到第24天之间增加了5倍。相比之下，肾脏中的TC mRNA水平在第4天到第12天增加了2.5倍，然后在第24天下降了2倍。成年大鼠肾上腺切除导致口服与胃内因子（IF）结合的[(57)Co]钴胺素（Cbl）复合物后，回肠中TC mRNA水平下降4倍，回肠黏膜中TC-[(57)Co]钴胺素（Cbl）复合物的形成下降50%。可的松治疗逆转了回肠中观察到的这些变化。与回肠不同，可的松治疗前后，肾上腺切除大鼠肾脏中的TC mRNA水平没有显著改变。综上所述，本研究为大鼠肾脏和肠道出生后发育过程中转钴胺素基因表达受到调控提供了证据，并且可的松选择性地调节回肠而非肾脏中的TC mRNA水平。
