Wald H, Popovtzer M M, Garty H
Nephrology Service, Hadassah University Hospital, Jerusalem, Israel.
Am J Physiol. 1997 May;272(5 Pt 2):F617-23. doi: 10.1152/ajprenal.1997.272.5.F617.
The channel-inducing factor (CHIF) is an epithelial-specific transmembrane protein, which is induced by aldosterone in distal colon (but not in kidney) and can evoke K+ conductance in Xenopus oocytes. The current study examined the possibility that CHIF participates in maintaining K+ balance by assessing its regulation during variations in K+ intake. In adrenal-intact rats, high-K+ diet stimulated, whereas K+ deficiency downregulated, CHIF mRNA both in kidney and colon. The downregulation of CHIF observed in rats fed a low-K+ diet for different periods of time closely correlated with a decrease in plasma K+ but also with changes in aldosterone levels. To differentiate between the two, modulation of CHIF has been studied in adrenalectomized rats with and without corticosteroid supplementation. These experiments have demonstrated that a low-K+ intake suppresses CHIF mRNA, irrespective of aldosterone level. On the other hand, the upregulation evoked by a high-K+ load is apparent only in adrenal-intact rats. This is despite the fact that infusing rats with aldosterone and corticosterone does not increase the expression of this mRNA in kidney. These findings may suggest a role for CHIF in preserving K+ balance.
通道诱导因子（CHIF）是一种上皮特异性跨膜蛋白，由醛固酮在远端结肠（而非肾脏）诱导产生，且能在非洲爪蟾卵母细胞中引发钾离子电导。当前研究通过评估钾离子摄入量变化时CHIF的调节情况，来探究CHIF参与维持钾离子平衡的可能性。在肾上腺完整的大鼠中，高钾饮食会刺激肾脏和结肠中的CHIF mRNA表达，而钾离子缺乏则会使其下调。在不同时间段喂食低钾饮食的大鼠中观察到的CHIF下调，与血浆钾离子的降低密切相关，也与醛固酮水平的变化有关。为区分两者，在补充和未补充皮质类固醇的肾上腺切除大鼠中研究了CHIF的调节情况。这些实验表明，低钾摄入会抑制CHIF mRNA，而与醛固酮水平无关。另一方面，高钾负荷引起的上调仅在肾上腺完整的大鼠中明显。尽管给大鼠输注醛固酮和皮质酮并不会增加该mRNA在肾脏中的表达。这些发现可能提示CHIF在维持钾离子平衡中发挥作用。
