REGULATING NA+/K+ ATPASE ISOFORMS DURING CARDIAC GROWTH

在心脏生长过程中调节 NA /K ATP酶异构体

• 批准号: 2219342
• 负责人: YUK-CHOW NG
• 金额: $ 19.11万
• 依托单位: PENNSYLVANIA STATE UNIV HERSHEY MED CTR
• 依托单位国家: 美国
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-08-01 至 1997-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2219342
• 关键词: enzyme structure; ferrets; fluorescence microscopy; gene expression; growth /development; heart cell; heart metabolism; hormone regulation /control mechanism; intracellular transport; isozymes; laboratory rat; membrane transport proteins; myocardium; newborn animals; rubidium; sodium; sodium potassium exchanging ATPase; thyroid hormones

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.

在心肌中，Na+,K+-ATP酶维持电化学梯度 因此，心肌细胞直接和间接调节电 和心脏的收缩活动。 Na+,K+-ATP酶由 存在多种亚型的 α 和 β 亚基，尽管 它们的生理功能仍不清楚。总体假设为 待测试的是心脏生长过程中心脏Na+、K+-的表达 ATP 酶同工酶受到不同程度的调节，并且各个同工酶 在调节细胞内 Na+ 浓度方面发挥独特的功能 ([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，后者表达 主要是 alpha1 和 alpha2 同工型。因此，雪貂提供了有用的 研究 alpha3 表达和功能的模型，其表达形式为 人类心脏以及 alpha1 和 alpha2。使用雪貂和大鼠作为 动物模型，将研究以下目标：1）表达 α3亚型在出生后早期发育期间上调。在 新生儿雪貂心脏，优先甲状腺激素（TH）治疗 上调 alpha3 同工型。将检验假设 TH 是 α3亚型表达的生理调节剂 发育性心脏生长。 基础转录和/或后转录 将检查转录机制。 2) 心肌由以下部分组成 功能异质的心肌细胞。本地化分布 同工型可以揭示同工酶的特殊功能。就地使用 杂交和免疫细胞化学，Na+,K+-ATP酶的分布 大鼠心肌发育生长过程中的亚型 雪貂将被建立。 3）泵的相对贡献 总体泵活性的亚型将在条件下确定 当细胞内 Na+ 负荷改变时，通过研究 Na 泵活性 通过荧光显微镜观察 86Rb+ 吸收和 [Na]i。 Na亲和力 通过测量 Na-，可以直接在分离的心肌细胞中检查同工酶 使用 86Rb+ 摄取的依赖泵活性。功能性后果 将检查发育期间改变的亚型表达。 一个 对调节、分布和功能的完整理解 Na+,K+-ATP酶同工酶在心脏生长过程中可能不仅有帮助 了解心肌的生理学和病理生理学， 还在于开发更好的使用心脏的临床策略 糖苷，Na+,K+-ATPase 是唯一已知的受体。