What is the clinical evidence from this study?

Study design: Other. Population: Healthy rats (n=36). Intervention: Low sodium diet vs. Normal sodium diet (1.6%). Primary outcome: Angiotensinogen mRNA levels in aortic medial smooth muscle (3.2-fold increase, p=<0.005).

April 1, 1991Journal of Clinical Investigation137 citationsOpen Access

Localization and differential regulation of angiotensinogen mRNA expression in the vessel wall.

Q: What are the key findings of this study?

A low sodium diet (0.02%) for 5 days increased angiotensinogen mRNA levels in the aortic medial smooth muscle of WKY rats by 3.2-fold (P < 0.005) compared to a 1.6% sodium diet, without affecting levels in periaortic fat.

ANAllen J. NaftilanBrigham and Women's Hospital WZW M ZuoChinese Academy of Medical Sciences & Peking Union Medical College JIJ InglefingerBrigham and Women's Hospital

Key Result

A low sodium diet (0.02%) for 5 days increased angiotensinogen mRNA levels in the aortic medial smooth muscle of WKY rats by 3.2-fold (P < 0.005) compared to a 1.6% sodium diet, without affecting levels in periaortic fat.

Structured PICO

Does dietary sodium regulate angiotensinogen mRNA expression in the blood vessel wall of rats?

Population

36 male Wistar and WKY rats, 10-12 weeks old, evaluated for the effect of dietary sodium on vascular angiotensinogen mRNA expression over 1 to 5 days.

Intervention

Low sodium diet (0.02% sodium) for 5 days

Comparator

1.6% sodium diet

Outcome

Angiotensinogen mRNA expression levels in the aortic medial smooth muscle layer and periaortic fatsurrogate

Dietary sodium differentially regulates angiotensinogen mRNA expression in the vascular smooth muscle versus periaortic fat in rats.

Main Result

Effect estimate: 3.2-fold increase

Absolute Event Rate: 3.2% vs 1%

p-value: p=<0.005

Limitations

The exact mechanism for dietary sodium-induced changes in aortic medial angiotensinogen mRNA expression is unclear.
More detailed experiments are needed to determine if changes occur via transcription, processing, transport, or mRNA stability.

Abstract

Recent data demonstrate the existence of a vascular renin angiotensin system. In this study we examine the localization of angiotensinogen mRNA in the blood vessel wall of two rat strains, the Wistar and Wistar Kyoto (WKY), as well as the regulation of vascular angiotensinogen mRNA expression by dietary sodium. Northern blot analysis and in situ hybridization histochemistry demonstrate that in both strains angiotensinogen mRNA is detected in the aortic medial smooth muscle layer as well as the periaortic fat. In WKY rats fed a 1.6% sodium diet, angiotensinogen mRNA concentration is 2.6-fold higher in the periaortic fat than in the smooth muscle, as analyzed by quantitative slot blot hybridization. Angiotensinogen mRNA expression in the medial smooth muscle layer is sodium regulated. After 5 d of a low (0.02%) sodium diet, smooth muscle angiotensinogen mRNA levels increase 3.2-fold (P less than 0.005) as compared with the 1.6% sodium diet. In contrast, angiotensinogen mRNA level in the periaortic fat is not influenced by sodium diet. In summary, our data demonstrate regional (smooth muscle vs. periaortic fat) differential regulation of angiotensinogen mRNA levels in the blood vessel wall by sodium. This regional differential regulation by sodium may have important physiological implications.

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