REGULATING NA+/K+ ATPASE ISOFORMS DURING CARDIAC GROWTH

在心肌中，Na+，K+-ATPase维持 因此，心肌细胞直接和间接地调制电 心脏的收缩活动。Na+，K+-ATPase由一个 α-和β-亚基，存在多种异构体，尽管 它们的生理功能尚不清楚。总体假设为 被检测的是心脏生长过程中心肌Na+、K+-的表达 ATPase同工酶是有差异调节的，而单个同工酶 在调节细胞内Na+浓度中发挥独特作用 ([NA]i)。雪貂心肌表达α3和α1亚型 与通常研究的成年大鼠心脏相比，它表达 主要是α1和α2亚型。因此，雪貂提供了一种有用的 研究Alpha3的表达和功能的模型，它在 人类心脏以及字母1和字母2。使用雪貂和老鼠作为 动物模型，将研究以下目标：1)表达 α3亚型的表达在出生后早期发育过程中上调。在……里面 新生儿雪貂心脏，甲状腺激素(TH)优先治疗 上调α3亚型。这一假设将得到检验，即这是 α3异构体表达的生理调节 心脏发育性生长。潜在转录和/或后转录- 我们将研究转录机制。2)心肌由以下组成 功能异质的心肌细胞。的本地化分布 同工酶的异构体可能揭示同工酶的特殊功能。在现场使用 Na~+，K~+-ATPase的杂交和免疫细胞化学分布 大鼠心肌发育发育过程中的异构体及 雪貂将被建立起来。3)泵的相对贡献 在有条件的情况下，将确定泵的总体活性的异构体 当细胞内Na+负荷改变时，通过研究钠泵的活性 ~(86)Rb+摄取和荧光显微镜下的[Na]i。NA的亲和力 同工酶将通过测量Na-来直接在分离的心肌细胞中检测。 86Rb+摄取依赖于泵的活性。中的函数后果 在发育过程中改变的异构体表达将被检测。一个 对政府部门的监管、分配和职能有全面的了解 心脏发育过程中的Na+，K+-ATPase同工酶可能不仅有助于 在了解心肌的生理学和病理生理学时， 而且还在开发更好的临床策略以使用心脏 糖苷，其中Na+，K+-ATPase是唯一已知的受体。

In myocardium, Na+,K+-ATPase maintains the electrochemical gradient of the cardiac cells, hence, directly and indirectly modulates electrical and contractile activity of the heart. Na+,K+-ATPase consists of an alpha- and a beta-subunit to which multiple isoforms exist, although their physiological function remains unclear. The overall hypothesis to be tested is that during cardiac growth expression of cardiac Na+,K+- ATPase isozyme is differentially regulated, and that individual isozymes serve unique function in regulating intracellular Na+ concentration ([Na]i). Ferret myocardium expresses alpha3 and alpha1 isoforms, in contrast to the commonly studied adult rat heart which expresses predominately alpha1 and alpha2 isoforms. Thus, ferrets provide a useful model to study expression and function of alpha3, which is expressed in human heart along with alpha1 and alpha2. Using ferrets and rats as animal models, the following objectives will be studied: 1) Expression of alpha3 isoform is upregulated during early postnatal development. In neonatal ferret heart, thyroid hormone (TH) treatment preferentially upregulates the alpha3 isoform. The hypothesis will be tested that TH is a physiological regulator in expression of the alpha3 isoform during developmental cardiac growth. Underlying transcriptional and/or post- transcriptional mechanisms will be examined. 2) Myocardium consists of functionally heterogenous myocardial cells. Localized distribution of the isoforms may reveal specialized function of the isozymes. Using in situ hybridization and immunocytochemistry, distribution of the Na+,K+-ATPase isoforms during developmental growth of the myocardium in rats and ferrets will be established. 3) Relative contribution of the pump isoforms to overall pump activity will be determined, under conditions when intracellular Na+ load is altered, by studying Na-pump activity by 86Rb+ uptake, and [Na]i by fluorescence microscopy. Na affinity of the isozymes will be examined directly in isolated myocytes by measuring Na- dependent pump activity using 86Rb+ uptake. Functional consequences in altered isoform expression during development will be examined. A complete understanding in regulation, distribution, and function of the Na+,K+-ATPase isozymes during cardiac growth may prove helpful not only in understanding the physiology and pathophysiology of the myocardium, but also in developing better clinical strategies for use of cardiac glycosides, to which Na+,K+-ATPase is the only known receptor.