Molecular research for developmental mechanism and gene therapy for hydrocephalus

利钠肽是刺激利钠、利尿和血管舒张活性的激素。C型利钠肽（CNP）是一种新发现的利钠肽家族成员，被认为主要是一种神经肽。基于这种想法，我们进行了一项测试，以确定CNP是否可以控制中枢神经系统中的电解质稳态和水含量。进行了四项实验研究。(1)在原代星形胶质细胞和神经胶质瘤U373细胞中使用免疫酶测定响应CNP的细胞内cGMP浓度。(2)有和无鸟苷酸环化酶-B受体（GC-B）cDNA的胶质瘤U373细胞对CNP的反应的细胞大小。(3)测量了脑室内推注CNP后先天性脑积水HTX大鼠（HTX）的颅内压变化。(4)用CNP放射免疫分析法测定HTX CSF中CNP的浓度，结果如下：(1)发现培养的星形胶质细胞中cGMP的产生取决于添加至培养基中的CNP浓度。(2)CNP处理导致具有GC-B受体的U373中细胞尺寸逐渐减小，从处理后5 mm开始，在30 mm后达到最大值。（3）脑室内注射CINIP可有效降低HTX的颅内压。(4)从无CSF循环障碍的HTX收集的CSF的CNP浓度为4.82 * 2.68 pg/ml，而脑积水HTX的CNP浓度为17.34 * 4.04 pg/ml。这些结果表明CNP通过CC-B受体调节星形胶质细胞中的离子和水转运。由于星形胶质细胞参与中枢神经系统的体积和离子控制，CNP可能作为调节中枢神经系统含水量和电解质稳态的关键激素发挥作用。此外，CNP可能是高颅内压药物治疗的候选药物之一。

The natriuretic peptides are hormones that stimulate natriuretic, diuretic and vasorelaxant activity. C-type natriuretic peptide (CNP), a newly identified member of the natriuretic peptide family, is thought to function mainly as a neuropeptide. With this mind, we conducted a test to determine whether CNP could control the electrolytes homeostasis and water content in the central nerve system. Four experimental investigations were carried out. (1) intracellular cGMP concentration using immunoenzyme assay in primary astrocytes and glioma U373 cells in response to CNP.(2) Cell size in glioma U373 cells with and without Guanylate Cyclase-B receptor (GC-B) cDNA in response to CNP.(3) Changes in intracranial pressure in congenital hydrocephalic HTX-rats (HTX) after bolus intraventricular CNP injection were measured. (4) CNP concentration in HTX CSF were measured by radioimmunoassay for CNP.The following results were obtained. (1) cGMP production in cultured astrocytes was found to be dependent on the concentrations of CNP added to the culture media. (2) CNP treatment results in gradual decrease of the cell size in U373 with GC-B receptor that starts 5 mm. after treatment and reaches the maximum after 30 mm.(3)Intraventricular injection of CINIP in HTX was found to be effective in lowering intracranial pressure. (4) CNP concentration of CSF collected from HTX with no disturbance of CSF circulation were 4.82 * 2.68 pg/ml and, while CNP concentration of hydrocephalic HTX were 17.34 * 4.04 pg/ml. These results suggest that CNP regulates ion and water transport via CC-B receptor in astrocytes. Since astrocytes are involved in the volume and ion control in the central nervous system, CNP may function as a key hormone regulating water content and electrolytes homeostasis in the central nervous system. Furthermore, CNP could be one candidate for medical treatment of high intracranial pressure.