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(Hypertension. 2003;42:369.)
© 2003 American Heart Association, Inc.

Scientific Contributions

Chronic Salt Loading Upregulates Expression of Adrenomedullin and Its Receptors in Adrenal Glands and Kidneys of the Rat

Yuan-Ning Cao; Kazuo Kitamura; Johji Kato; Kenji Kuwasako; Kaoru Ito; Hisamitsu Onitsuka; Yasuko Nagoshi; Tomohiko Uemura; Toshihiro Kita; Tanenao Eto

From the First Department of Internal Medicine, Miyazaki Medical College, Miyazaki, Japan; and the Department of Food Science and Technology (K.I.), Minami-Kyusyu University, Miyazaki, Japan.

Correspondence to Tanenao Eto, MD, First Department of Internal Medicine, Miyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan. E-mail keto{at}post.miyazaki-med.ac.jp

The vasodilator peptide adrenomedullin (AM) elicits diuresis and natriuresis and inhibits aldosterone secretion. The aim of this study was to better understand the role of AM in maintaining water and electrolyte balance during chronic salt loading. Male Wistar rats were divided into a high salt (HS) group that received a diet containing 8% sodium chloride (NaCl) and a normal salt group that received a diet containing 0.4% NaCl. Plasma AM concentrations as well as expression of AM mRNA in the adrenal gland and kidney were then measured after 3, 7, 14, and 28 days. After 28 days, sodium and water excretion were significantly higher in HS rats than in control, although blood pressure and fluid volume were not significantly affected. Moreover, although plasma AM remained unchanged for up to 14 days, it was increased 2.5-fold in HS rats after 28 days on a high salt diet, and there were corresponding 3-fold and 1.5-fold increases in the levels of AM mRNA in the adrenal gland and kidney, respectively. At the same time, expression of calcitonin receptor-like receptor mRNA was significantly upregulated in both kidney and adrenal gland, as was expression of receptor activity-modify protein 1 (RAMP1) and RAMP2 mRNA in the adrenals and expression of RAMP3 in kidneys. Taken together, these results suggest that AM plays a role in the regulation of water and electrolyte balance in animals chronically ingesting high levels of salt.

Key Words: adrenomedullin • diuresis • natriuresis • gene expression • sodium

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