Takayama M, Nonoguchi H, Yang T, Machida K, Terada Y, Owada A, Tomita K, Marumo F
2nd Department of Internal Medicine,Tokyo Medical and Dental University, Tokyo, Japan.
Exp Nephrol. 1999 Jul-Aug;7(4):295-305. doi: 10.1159/000020617.
We investigated acute and chronic effects of hyperosmolality on mRNA and protein expressions of Na-K-ATPase alpha and beta isoforms and Na-K-ATPase activity in the rat inner medullary collecting duct (IMCD). Incubation of IMCD in hypertonic medium for 30 min reduced the Na-K-ATPase activity by 50%. The Na-K-ATPase activity of dehydrated rats measured in isotonic medium was decreased, and incubation in hypertonic medium did not further decrease the activity. Incubation of IMCD in hypertonic medium for 6 h did not change alpha(1) mRNA. In contrast, dehydration decreased alpha(1) subunit mRNA and protein and beta(1) protein expressions without changing beta(1) mRNA. These data show (1) that acute hyperosmolality decreases Na-K-ATPase activity in IMCD without changing alpha(1) and beta(1) mRNA and (2) that 2 days of dehydration decreased Na-K-ATPase activity by reducing alpha(1) and beta(1) proteins. Thus, the mechanisms for the inhibition of the Na-K-ATPase activity in IMCD is different between acute and chronic exposure to hyperosmolality.
我们研究了高渗对大鼠髓质内层集合管（IMCD）中钠钾ATP酶α和β亚型的mRNA和蛋白表达以及钠钾ATP酶活性的急性和慢性影响。将IMCD在高渗培养基中孵育30分钟可使钠钾ATP酶活性降低50%。在等渗培养基中测量的脱水大鼠的钠钾ATP酶活性降低，而在高渗培养基中孵育并未进一步降低该活性。将IMCD在高渗培养基中孵育6小时不会改变α(1) mRNA。相反，脱水会降低α(1)亚基mRNA和蛋白以及β(1)蛋白的表达，而不会改变β(1) mRNA。这些数据表明：（1）急性高渗会降低IMCD中的钠钾ATP酶活性，而不会改变α(1)和β(1) mRNA；（2）两天的脱水通过降低α(1)和β(1)蛋白来降低钠钾ATP酶活性。因此，急性和慢性暴露于高渗环境时，IMCD中钠钾ATP酶活性受到抑制的机制是不同的。
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