Role of H,K-ATPase in the Action of Mineralocorticoids

描述(由申请人提供)： 在美国，心血管疾病是主要的死亡原因。系统性动脉高血压(或简称“高血压”)是心血管疾病发展的主要危险因素。醛固酮和脱氧皮质酮(DOC)是一种盐皮质激素，通过增加尿钠(Na)滞留而导致高血压，并通过更大的尿酸化导致低血钾性代谢性碱中毒。矿质皮质激素通过影响远端肾单位和集合管(Cd)离子的运输来实现这些作用。CD表达至少两种H，K-ATPase亚型，HK？1和HK？2，参与CD的酸分泌。我们最近的研究还表明，长期服用DOC除草剂(DOCP)可刺激肾脏钠滞留、体重增加和代谢性碱中毒，这些作用依赖于H，K-ATPase的存在。具体地说，缺乏H，KATPase(HK？1，2-/-)的小鼠未能对DOCP刺激产生显著的钠滞留或代谢性碱中毒。比较了单HK？1-/-对双HK？1，2-/-的反应，强烈表明H，K-ATPase HK？2亚型在DOCP的反应中起着重要的生理作用。因此，我们的中心假设是：A)H，K-ATPase HK？2亚型对于盐皮质激素的慢性作用是关键的，从而产生肾脏钠滞留，引起低血钾性代谢性碱中毒，并升高血压；B)饮食K负荷取消或减弱了矿质皮质激素对钠滞留和电解质异常的作用，这依赖于肾脏H，K-ATPase HK？2亚型的诱导。我们提出了以下具体目标：1)确定H，K-ATPase HK？2亚型在慢性糖皮质激素治疗后离子转运反应中的作用；2)确定H，K-ATPase HK？2亚型在血压调节中的作用以及K摄入量和低钾血症对这些变化的贡献；3)确定WT和HK？2KO动物对DOCP治疗的反应差异是否反映了肾脏表型。我们将验证这一新的生理学假说，即H，K-ATPase HK？2亚型在钠稳态、容量调节和血压控制中具有重要作用。因此，我们开发了一种结合整体动物代谢平衡研究、体外微灌流、最先进的血压无线电遥测和肾移植的综合方法，以研究矿质皮质激素对HK？2刺激的生理意义。

DESCRIPTION (provided by applicant): Cardiovascular disease is the leading cause of death in the United States. Systemic arterial hypertension (or simply "hypertension") is a major risk factor for the development of cardiovascular disease. Aldosterone and desoxycorticosterone (DOC) are mineralocorticoids that cause hypertension through increased urinary sodium (Na) retention and hypokalemic metabolic alkalosis through greater urinary acidification. Mineralocorticoids affect distal nephron and collecting duct (CD) ion transport to achieve these effects. The CD expresses at least two isoforms of H,K-ATPases, HK¿1 and HK¿2, that participate in acid secretion by the CD. Our recent studies also show that chronic DOC pivalate (DOCP) administration stimulates renal Na retention, weight gain, and metabolic alkalosis that are dependent on the presence of H,K-ATPases. Specifically, mice that lack both H,KATPases (HK¿1,2 -/-) failed to develop significant Na retention or metabolic alkalosis in response to DOCP stimulation. Comparison of the response of the single HK¿1 -/- to the double HK¿1,2 -/- strongly suggests an important physiological role for the H,K-ATPase HK¿2 isoform in the response to DOCP. Therefore, our central hypotheses are that: A) the H,K-ATPase HK¿2 isoform is critical for the chronic action of mineralocorticoids to produce renal Na retention, cause hypokalemic metabolic alkalosis, and increase blood pressure (BP); and that B) dietary K loading abolishes or attenuates mineralocorticoid action on Na retention and electrolyte abnormalities, which are dependent on the induction of the H,K-ATPase HK¿2 isoform in the kidney. We propose the following specific aims: 1) to determine the role of the H,K-ATPase HK¿2 isoform in the ion transport response to chronic mineralocorticoid treatment; 2) to determine the role of H,K-ATPase HK¿2 isoform in the regulation of blood pressure and the contribution of K intake and hypokalemia to these changes; 3) to determine if the differences in WT and HK¿2 KO animals in response to DOCP administration reflect a renal phenotype. We will test the novel physiological hypothesis that the H,K-ATPase HK¿2 isoform has an important role in Na homeostasis, volume regulation and BP control. As such, we have developed an integrated approach that combines whole animal metabolic balance studies, in vitro microperfusion, state-ofthe- art radiotelemetry measurement of BP, and renal transplantation to examine the physiological significance of HK¿2 stimulation by mineralocorticoids.