CHEMICAL STRUCTURE OF HYPOTHALAMIC NA/K ATPASE INHIBITOR

最近的实验表明，可能存在一种内源性哺乳动物 洋地黄苷的类似物，可以调节哺乳动物 Na/K-ATPase(钠泵)是生理学的而不是药理学的。 这种化合物被认为与控制肾脏钠的排泄有关， 心肌中的正性肌力作用，并可能在 高血压是人类一种常见疾病的发病机制。一次高潮 哺乳动物Na/K-ATPase的亲和力、特异性、可逆性抑制物 已从牛下丘脑中完全提纯。这个下丘脑 抑制因子，HIF，具有相似的生物学特性，但不是 与强心苷、哇巴因相同，且一致 在体内进行生理调节。黄曲霉毒素的物理化学表征 HIF表明哇巴因和HIF都被发现是α-L 鼠李糖苷，它们的苷元部分在结构上是不同的。 这种结构性差异被推定为解释了观察到的 HIF和哇巴因生物学特性的差异。目标 目前的建议是(1)提纯几微克的HIF， 利用既定程序；(2)使用纯HIF来确定 液-质联用和圆二色谱 哇巴因和缺氧诱导因子的苷元是否 立体化学上相同的；(3)如果它们不相同，则进一步使用 光谱学研究确定了HIF-苷元的立体化学； 以及(4)如果它们相同，则合成位置异构体以测试 生物活性产品。这项工作的成功将定义 特定的结构差异在药物抑制剂， 哇巴因，以及可能的哺乳动物生理类似物HIF。知道 HIF的确切结构是可取的，因为它可能会揭示 提高心力衰竭治疗指数的一般策略 糖苷类物质，为研究内源激素的作用提供了一种探索。 Na/K-ATPase抑制在高血压发病机制中的作用 疾病。

Recent experiments suggest that there might be an endogenous mammalian analogue to the digitalis glycosides which would regulate the mammalian Na+/K+-ATPase (Na+ pump) in a physiologic rather than pharmacologic way. Such a compound has been linked to control of renal Na+ excretion, positive inotropic effects in cardiac muscle, and may play a role in the pathogenesis of a prevalent human disease, hypertension. A high affinity, specific, reversible inhibitor of the mammalian Na+/K+-ATPase has been completely purified from bovine hypothalamus. This hypothalamic inhibitory factor, HIF, has biological properties similar to, but not identical to, those of the cardiac glycoside, ouabain, and consistent with physiologic regulation in vivo. Physiochemical characterization of HIF indicates that while both ouabain and HIF are found to be alpha-L rhamnosides, they are structurally different in their aglycone portions. This structural difference is presumed to account for the observed differences in the biological properties of HIF and ouabain. The aims of the current proposal are (1) to purify several micrograms of HIF, utilizing established procedures; (2) to use the pure HIF to determine by liquid chromatography/mass spectrometry and circular dichroism spectrometry whether the aglycones of ouabain and HIF are stereochemically identical; (3) if they are not identical, to use further spectroscopic studies to assign the sterochemistry of the HIF-aglycone; and (4) if they are identical, to synthesize position isomers testing the products for biological activity. Success in this work would define the specific structural difference between the pharmacologic inhibitor, ouabain, and the putative mammalian physiologic analogue, HIF. Knowing the exact structure of HIF is desirable since it would probably reveal a general strategy for improving the therapeutic index of cardiac glycosides, and provide a probe to study the proposed role of endogenous Na+/K+-ATPase inhibition in the pathogenesis of human hypertensive disease.