肾脏（钠+钾）-三磷酸腺苷酶活性对甲状腺状态的依赖性。

Dependence of renal (Na+ + k+)-adenosine triphosphatase activity on thyroid status.

作者信息

Lo S C, August T R, Liberman U A, Edelman I S

出版信息

J Biol Chem. 1976 Dec 25;251(24):7826-33.

Abstract

In thyroidectomized rats, a single injection of L-2,,5,2'-triiodothyronine (T3) (50mug/100 g body weight) elicited at 45% increase in (Na+ + k+)-dependent adenosine triphosphatase (NaK-ATPase) activity of the membrane-rich fraction of renal cortex at the optimal time of response, 48 h after injection. Three successive doses of T3 (50 mug/100 g body weight), given on alternate days, increased NaK-ATPase by 67% in the renal cortex but had no significant effect on the outer medulla or the papilla. Moreover, T3 had no effect on Mg2+-dependent adenosine trisphatase (MgATPase) in cortex, cedulla, or papilla. Three doses of T3 (50 mug/100 g body weight) given on alternate days to thyroidectomized rats elecited a 134, 79, and 46% increase in Vmax for ATP, Na4, and K+, respectively. There were no changes in the Km for ATP or the K1/2 values for Na+ and K+. Two methods were used to estimate the effect of T3 on the number of NaK-ATPase units (assumed to represent the number of Na+ pump sites); rat renal plasma membrane fractions were incubated with [gamma-32P]ATP, Mg2+, and Na+; the 32P-labeled membrane protein yeild was quantitatively dependent on Na+ and was hydrolyzed on addition of K+. There was a linear correlation between the specific activity of NaK-ATPase (Vmax) and the amount of phosphorylated intermediate formed, in renal cortical membrane fractions from thyroidectomized rats given T3 or the diluent. There was also a linear correlation between the specific activity of NaK-ATPase (Vmax) and the amount of [3H]ouabain specifically bound (Na+-, Mg2+-, APT-dependent) to the NaK-ATPase preparation. Injection of T3 resulted in a 70% increase in NaK-ATPase activity, a 79% increase in formation of the phosphorylated intermediate, and a 65% increase in the [H]ouabain specifically bound to the NaK-ATPase system. The T3-dependent increases in Vmax for ATP, Na+, and K+ and the proportionate increases in the phosphorylated intermediate and in the amount of [3H]ouabain bound indicate that T3 increases the number of NaK-ATPase units and that this increase accounts for the increase in NaK-ATPase activity.

摘要

在甲状腺切除的大鼠中，单次注射L-2,5,2'-三碘甲状腺原氨酸（T3）（50μg/100g体重）在注射后48小时（最佳反应时间）使肾皮质富含膜部分的（Na⁺+K⁺）依赖性三磷酸腺苷酶（NaK-ATPase）活性增加45%。每隔一天给予三次连续剂量的T3（50μg/100g体重），使肾皮质中的NaK-ATPase增加67%，但对髓质外层或乳头无显著影响。此外，T3对皮质、髓质或乳头中的Mg²⁺依赖性三磷酸腺苷酶（MgATPase）无影响。每隔一天给甲状腺切除的大鼠注射三次剂量的T3（50μg/100g体重），分别使ATP、Na⁺和K⁺的Vmax增加134%、79%和46%。ATP的Km以及Na⁺和K⁺的K1/2值没有变化。使用两种方法来估计T3对NaK-ATPase单位数量（假定代表Na⁺泵位点数量）的影响；将大鼠肾质膜部分与[γ-³²P]ATP、Mg²⁺和Na⁺一起孵育；³²P标记的膜蛋白产量在数量上依赖于Na⁺，并在加入K⁺后被水解。在给予T3或稀释剂的甲状腺切除大鼠的肾皮质膜部分中，NaK-ATPase的比活性（Vmax）与形成的磷酸化中间体的量之间存在线性相关性。NaK-ATPase的比活性（Vmax）与特异性结合到NaK-ATPase制剂上的[³H]哇巴因的量（Na⁺、Mg²⁺、ATP依赖性）之间也存在线性相关性。注射T3导致NaK-ATPase活性增加70%，磷酸化中间体的形成增加79%，以及特异性结合到NaK-ATPase系统上的[³H]哇巴因增加65%。T3依赖性的ATP、Na⁺和K⁺的Vmax增加以及磷酸化中间体和结合的[³H]哇巴因量的相应增加表明，T3增加了NaK-ATPase单位的数量，并且这种增加解释了NaK-ATPase活性的增加。