Changes in renin and atrial natriuretic polypeptude mRNA levels.

本研究观察了不同钠摄入量大鼠和自发性高血压大鼠（SHR）血浆中肾素、血管紧张素原和心钠素（ANP）基因的表达。用放射密度cDNA杂交法检测血管紧张素原和心钠素的mRNA表达。为了测定肾肾素mRNA，使用含有大鼠肾素基因的最后一个外显子的760个碱基对的Rsa I片段作为放射密度测定的探针。在高钠状态下，血浆肾素浓度（PRC）、肾脏肾素浓度（RRC）和肾脏肾素mRNA分别下降88%、90%和75%。在低钠状态下，PRC、RRC和肾素mRNA分别增加17倍、2.5倍和4.5倍。在钠耗竭过程中给予卡托普利治疗，PRC和肾素mRNA分别增加144倍和17.1倍，RRC增加4.2倍。在高钠状态下，肝脏和肾脏中的血管紧张素原mRNA水平降低，在低钠状态下增加，程度相似。Captopril治疗降低了约一半的两个器官中的血管紧张素原mRNA。血浆ANP和ANP mRNA在低钠状态下比高钠状态下降低，而心房ANP含量在低钠和高钠状态下均不变。这些结果表明，钠摄入量影响的表达的肾素，血管紧张素原和心钠素基因。在4、8、12、16周龄SHR和Wistar京都大鼠（SHR）中，SHR的PRA和PAC与WKY无显著差异。SHR和WKY大鼠肾脏肾素mRNA和心房心钠素mRNA水平无明显变化。提示肾性肾素和心房心钠素可能不参与血压升高。

The expressions of the renin, angiotensinogen and atrial natriuretic polypeptide (ANP) genes were studied in rats with varying sodium intakes and the spontaneously hypertensive rats (SHR). Messenger RNA (mRNA) for angiotensinogen and ANP was measured by a sensitive radiodensitometric cDNA hybridization assay. For the determination of renal renin mRNA, the 760-base pair Rsa I fragment containing the last exon of the rat renin gene was used as a probe for a radiodensitometric assay. In the high sodium state, plasma renin concentration (PRC), renal renin concentration (RRC) and renal renin mRNA decreased by 88% , 90% and 75% respectively. In the low sodium state,PRC,RRC,and renin mRNA increased 17-fold,2.5-fold and 4.5-fold respectively. With captopril treatment during sodium depletion, PRC and renin mRNA increased 144-fold and 17.1-fold respectively, and RRC increased 4.2-fold. The angiotensinogen mRNA level in the liver and kidney decreased in the high sodium state and increased in the low sodium state to similar extents. Captopril treatment decreased angiotensinogen mRNA in both organs by about half. Plasma ANP and ANP mRNA decreased in the low sodium state compared to the high sodium state, while atrial ANP content was unaltered in both low and high sodium states. These results demonstrate that sodium intake affects the expression of the renin, angiotensinogen and ANP genes. In both SHR and Wistar Kyoto rats (SHR) that were 4,8,12 and 16 weeks of age, PRA and PAC in SHR did not differ from these in WKY. Renal renin mRNA level and ANP mRNA level in the atrium did not change in both SHR and WKY. These data suggested that renal renin and atrial ANP may not contribute to increase the blood pressure.