Drewnowsk K D, Craig M R, Digiovanni S R, McCarty J M, Moorman A F M, Lamers W H, Schoolwerth A C
Department of Medicine, Virginia Commonwealth University, Richmond 23298-0160, USA.
J Physiol Pharmacol. 2002 Mar;53(1):3-20.
To identify the nephron segments expressing PEPCK in control and acidotic conditions, PEPCK mRNA was localized in rat kidney using the technique of reverse transcription and polymerase chain reaction (RT-PCR) in individual microdissected S1 S2, and S3 segments of the rat proximal tubule. In controls, the number of tubules expressing PEPCK mRNA was greatest in the S3 segment, moderate in the S2 segment, and least in the S1 segment of the proximal tubule. After NH4Cl feeding, strong signals for PEPCK mRNA were detected in all three proximal tubule segments. In situ hybridization demonstrated expression of PEPCK mRNA only in the medullary rays in controls. After NH4Cl, PEPCK mRNA was expressed throughout the cortex, confirming the RT-PCR results. These data demonstrate the ability of the rat kidney cortex to modulate the expression of PEPCK mRNA during metabolic acidosis by recruitment of additional cells in the proximal nephrons. Studies with cultured LLC-PK1-F+ cells indicated that increased PEPCK gene transcription at acid pH required a cis-acting element (enhancer) in the more distal 5' flanking region of the promoter.
为了鉴定在对照和酸中毒条件下表达磷酸烯醇式丙酮酸羧激酶（PEPCK）的肾单位节段，利用逆转录和聚合酶链反应（RT-PCR）技术，在大鼠近端小管的单个显微切割的S1、S2和S3节段中对大鼠肾脏中的PEPCK mRNA进行定位。在对照中，表达PEPCK mRNA的小管数量在近端小管的S3节段最多，在S2节段中等，在S1节段最少。给予氯化铵后，在所有三个近端小管节段均检测到PEPCK mRNA的强信号。原位杂交显示在对照中PEPCK mRNA仅在髓放线中表达。给予氯化铵后，PEPCK mRNA在整个皮质中表达，证实了RT-PCR结果。这些数据表明，在代谢性酸中毒期间，大鼠肾皮质能够通过募集近端肾单位中的额外细胞来调节PEPCK mRNA的表达。对培养的LLC-PK1-F+细胞的研究表明，酸性pH下PEPCK基因转录的增加需要启动子更远端5'侧翼区域中的顺式作用元件（增强子）。
