Joint Study on the Function of Renin-binding Protein

肾素结合蛋白（renin -binding protein, RnBP）是一种与肾素结合的蛋白质，形成一种称为高分子量肾素的蛋白质复合物。采用Northern blot杂交技术检测RnBP在大鼠主动脉组织中的基因表达，探讨其生理功能。RnBP基因在大鼠主动脉、肾脏、肾上腺、脑和卵巢中均有表达。Northern blot杂交分析显示，来源于procine主动脉的动脉内皮细胞表现出高水平的RnBP基因表达。为了研究肾素基因与RnBP基因表达的关系，采用RT-PCR方法对猪肾mRNA进行分析，分离猪肾素cDNA片段，并测定猪肾素的核苷酸序列。最后，对内皮细胞中肾素mRNA的RT-PCR分析表明，肾素基因在同一内皮细胞中也有表达。在培养的内皮细胞中，RnBP基因表达被血管紧张素II （AII）和tgf - β上调，而不被tnf - α上调。因此，AII对肾素和RnBP的相互调节提示RnBP可能作为血管肾素-血管紧张素系统的一员参与血管内皮的血压调节。我们也证明了肾素-血管紧张素系统存在于肾上腺肾小球细胞内。此外，我们还获得了肾小球带线粒体致密体内存在肾素的免疫细胞化学和生化证据。

Renin-binding protein (RnBP) is a protein that binds to renin, forming a protein complex called high molecular weight renin. In search of its physiological function, gene cxpression of RnBP in rat aorta were examined by Northern blot hybridization. RnBP gene expression was observed in rat aorta, in addition to kidney, adrenal gland, brain and ovary. The arterial endothelial cells derived from procine aorta exhibited high level of RnBP gene expression, detected by Northern blot hybridization analysis. In order to study renin gene expression in relation to that of RnBP,porcine renin cDNA fragment was isolated by RT-PCR analysis of porcine kidney mRNA,followed by determination of the nucleotide sequence for porcine renin. Finally, the RT-PCR analysis of porcine renin mRNA in endothelial cells has shown that renin gene is also expressed in the same endothelium. RnBP gene expression was shown to be up-regulated by Angiotensin II (AII) and TGF-beta, but not by TNF-alpha in cultured endothelial cells. Therefore, reciprocal regulation of renin and RnBP by AII suggests that RnBP may participate in blood prressure regulation at vascular endothelium as a member of vascular renin-angiotensin system. We also demonstrate that an intracellular renin-angiotensin system exists in adrenal glomerulosa cells. Moreover we obtained immunocytochemical and biochemical evidence for the presence of renin within intaramitochondrial dense bodies of the zona glomerulosa.