Na-PUMP GENE EXPRESSION IN HYPERTROPHIC HEARTS

Na，K-ATPase(Na，K-泵)通过跨细胞膜运输Na+和K+来维持细胞内的离子组成，在许多基本的细胞和生理过程中发挥着重要的作用，如控制收缩、兴奋性和细胞体积调节。Na，K-ATPase蛋白由两个亚基组成，一个大的催化α亚基和一个较小的糖基化的β亚基。在大鼠和人类中，至少有三种α亚基异构体，即α1、α2和α3，以及两种β亚基异构体，即β1和β2。在科学研究资助计划(A)的支持下，我们发现；(2)在自发性高血压大鼠(SHR)肥厚的心脏中，4周龄高血压前期Na，K-ATPase基因的表达高于正常血压大鼠(WKY)；(3)在体内衰竭的叙利亚仓鼠心脏(Bio14.6)中，心肌Na，K-ATPase基因的表达与正常仓鼠(FLB)相比下调。因此，Na，K-ATPase基因表达的改变可能在心肌肥厚和心肌病的发病机制中起重要作用。

Na, K-ATPase (Na, K-pump) maintains intracellular ion composition by transporting Na^+ and K^+across the cell membrance, and plays an important role in many fundamental cellular and physiological processes such as the control of contractility, excitability, and cell volume regulation. The Na, K-ATPase protein comprises two subunits, a large catalytic alpha subunit and a smaller glycosylated beta subunit. At least three alpha subunit isoforms, alpha1, alpha2 and alpha3, and two beta subunit isoforms, beta1 and beta2, have been characterized in rats and humans. With the support of the Grant-in-Aid fro Scientific Research (A), we have revealed that ; (1) The expression of Na, K-ATPase alpha and beta subunits in cardiocytes in vitro was directly regulated at a transcriptional level by thyroid and aldosterone hormones, or Na^+, (2) In the hypertrophic hearts of spontaneously hypertensive rats (SHR), Na, K-ATPase mRNA expression was augmented compared with normotensive rats (WKY) at the pre-hypertensive stage of 4-week-old, (3) In the in vivo failing hearts of Syrian hamsters (Bio14.6), the expression of cardiac Na, K-ATPase gene was down-regulated compared with normal hamsters (Flb). Thus the alterations of Na, K-ATPase gene expression might play an important roll in the pathogenesis of cardiac hypertrophy and cardiomyopathy.