Changes in renin and atrial natriuretic polypeptude mRNA levels.

研究了不同钠摄入量大鼠和自发性高血压大鼠肾素、血管紧张素原和心房利钠多肽（ANP）基因的表达。采用灵敏的放射密度杂交法测定血管紧张素原和ANP的信使RNA （mRNA）。为了测定肾素mRNA，使用含有大鼠肾素基因最后外显子的760碱基对Rsa I片段作为探针进行放射性密度测定。在高钠状态下，血浆肾素浓度（PRC）、肾肾素浓度（RRC）和肾肾素mRNA分别降低88%、90%和75%。在低钠状态下，PRC、RRC和肾素mRNA分别增加了17倍、2.5倍和4.5倍。在钠耗竭期间，卡托普利组PRC和renin mRNA分别增加144倍和17.1倍，RRC增加4.2倍。肝、肾血管紧张素原mRNA水平在高钠状态下呈下降趋势，在低钠状态下呈上升趋势。卡托普利治疗可使两个器官的血管紧张素原mRNA减少约一半。与高钠相比，低钠状态下血浆ANP和ANP mRNA含量降低，而心房ANP含量在低钠和高钠状态下均未发生变化。这些结果表明，钠摄入量影响肾素、血管紧张素原和ANP基因的表达。在4、8、12和16周龄的SHR和Wistar Kyoto大鼠（SHR）中，SHR组的PRA和PAC与WKY组无显著差异。SHR组和WKY组大鼠心房肾素mRNA和ANP mRNA水平无明显变化。这些数据提示肾素和心房ANP可能不会导致血压升高。

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.