CONTROL OF ANF PRODUCTION IN HYPERTENSION

哺乳动物的心脏心房含有一组具有生物活性的 称为心钠素(ANF)的多肽。心房肌注射 提取或纯ANF对动物造成快速发病 利钠、利尿、降血压。这个 哺乳动物ANF基因由三个外显子组成，由两个外显子隔开 内含子。最初的转录本是前体ANF mRNA(前- ANF信使核糖核酸)，并被加工成心钠素信使核糖核酸 编码152个氨基酸的前体(Pre-Pro-ANF)，包含一个24 氨基酸信号序列。前PRO ANF被快速切割 生产PRO-ANF，加工成ANF并释放为ANF 发行量。这里描述的实验将尝试 找出可能对调节 ANF基因转录，转录后加工， 心钠素前体的合成及其在心房分泌的实验研究 体外心脏灌流，技术。心钠素前基因表达的速率 合成将基于将(~3H)尿苷掺入 在标记呈线性上升的时期， 和UTP的比活性，并且当稳定状态是 达到，(~3H)UMP在心钠素前的mRNA.加工率 ANF信使核糖核酸将基于纳入的放射性 心力衰竭前心钠素基因表达与(~3H)UMP比活性的关系 MRNA.ANF前mRNA合成的相对速率也将 通过分离的细胞的体外径流转录来估计 原子核。Pro-ANF的合成速率将基于 将(~3H)-苯丙氨酸(Phe)掺入亲心钠素， (~3H)-Phe-tRNA在不同时间的比活力 Pro-ANF的标记率呈线性上升，并保持稳定 ~(3 H)-Phe-tRNA比活度与酶活性的关系 (~3H)-Phe在亲ANF中。分泌物的速度将由 灌流液中ANF的出现。胰岛素的作用， 氨基酸利用率，左房充盈压，乙酰胆碱， 加压素、去甲肾上腺素和地塞米松对 转录、合成前心钠素和分泌心钠素将是 检查过了。最后，测定心房肌ANF mRNA的总含量，以及 血浆心钠素水平及心钠素前合成率 将测量mRNA和前ANF以及ANF的分泌 盐负荷大鼠心房与容量依赖性高血压 老鼠。这些定量的方法将有助于更多地了解 心房和血浆ANF水平是怎样的 在正常和高血压条件下受控。

Mammalian cardiac atria contain a group of biologically active peptides called atrial natriuretic factor (ANF). Injection of atrial extract or pure ANF to animals causes a rapid onset of natriuresis, diuresis and lowering of blood pressure. The mammalian ANF gene contains three exons separated by two introns. The primary transcript is precursor ANF mRNA (pre- ANF mRNA) and is processed to ANF mRNA, which in turn encodes a 152 amino acid precursor (pre-pro-ANF) containing a 24 amino acid signal sequence. The pre-pro ANF is rapidly cleaved to produce pro-ANF which is processed to ANF and released into circulation. The experiments described herein will attempt to identify the factors that may be important in regulating the transcription of ANF gene, post-transcriptional processing, synthesis of pro-ANF and secretion of ANF from atria using the in vitro heart perfusion, techniques. Rates of pre-ANF mRNA synthesis will be based on the incorporation of (3H) uridine into pre-ANF mRNA during the period when labeling is rising linearly, and the specific activity of UTP, and, when a steady state is reached, (3H) UMP in pre-ANF mRNA. Rates of processing of ANF mRNA will be based on the radioactivity incorporated into ANF mRNA and the specific activity of (3H) UMP in pre-ANF mRNA. The relative rates of pre-ANF mRNA synthesis will also be estimated by the in vitro run-off transcription of the isolated nuclei. Rates of pro-ANF synthesis will be based on the incorporation of (3H)-phenylalanine(phe) into pro-ANF, the specific activity of (3H)-phe-tRNA during the period when labeling of pro-ANF is rising linearly and the steady-state relationship between specific activities of (3H)-phe-tRNA and (3H)-phe in pro-ANF. Rates of secretion will be estimated by the appearance of ANF in the perfusate. The effects of insulin, amino acid availability, left-atrial filling pressure, acetylcholine, vasopressin, norepinephrine and dexamethasone on the transcription, synthesis of pro-ANF and secretion of ANF will be examined. Finally, total contents of atrial ANF mRNA, and plasma level of ANF, as well as rates of synthesis of pre-ANF mRNA and pro-ANF and secretion of ANF will be measured in atria from salt-loading rats and volume-dependent hypertensive rats. These quantitative methods will help to understand more completely how the atrial and plasma levels of ANF are controlled under normal and hypertensive conditions.