Intracellular Sodium Modulates the Expression of Angiotensin II Subtype 2 Receptor in PC12W Cells

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 33; no. 2; pp. 626 - 632
• Main Authors: Tamura, Masaaki, Wanaka, Yoshio, Landon, Erwin J, Inagami, Tadashi
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01-02-1999; Hagerstown, MD Lippincott
• Subjects: Angiotensin II - metabolism; Animals; Biological and medical sciences; Endocrine kidney. Renin-angiotensin-aldosterone system; Fundamental and applied biological sciences. Psychology; Ion Channels - metabolism; PC12 Cells; Rats; Receptors, Angiotensin - metabolism; Signal Transduction; Sodium - metabolism; Up-Regulation; Vertebrates: endocrinology; Cell culture; Ligand binding; Peptides; Rat; Rodentia; Gene expression; In vitro; Vertebrata; Regulation(control); Renin angiotensin system; Mammalia; Cell line; Sodium; Animal; Intracellular; Angiotensin II; Subtype; Biological receptor
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.hyp.33.2.626

Although the angiotensin II subtype 2 receptor (AT2-R) is expressed abundantly in the adrenal medulla, its physiological significance has not yet been determined. To obtain fundamental knowledge of the regulation of AT2-R expression in the adrenal medulla, we investigated the effects of modulating several ion channels on AT2-R expression in PC12W cells. Experiments were performed after 24 hours of serum depletion under subconfluent conditions. After 48 hours of treatment with various agonists or antagonists, the receptor density and mRNA level of AT2-Rs were quantified by I-[Sar,Ile]angiotensin II binding and Northern blot analysis. Ouabain (10 to 100 nmol/L) and insulin (10 to 100 nmol/L) dose-dependently increased receptor density and mRNA level. Analysis of the binding characteristics revealed that the ouabain-dependent increase in AT2-R levels was due to an increase in binding capacity without a change in the Kd value. These increases were blocked by lowering the Na concentration in the medium. A low concentration of the sodium ionophore monensin (10 nmol/L), the K blocker quinidine (10 [micro sign]mol/L), and the ATP-sensitive K blockers tolbutamide (100 [micro sign]mol/L) and glybenclamide (10 [micro sign]mol/L) also significantly increased receptor density, but the ATP-sensitive K agonist cromakalim (100 [micro sign]mol/L) decreased receptor density significantly (P<0.01). Nifedipine (10 [micro sign]mol/L) decreased basal receptor density and completely blocked the increase in receptor density caused by these agents. The increase in receptor density caused by an increase in intracellular Na was accompanied by an increase in mRNA level, whereas the ATP-sensitive K blockers did not change mRNA level. Nifedipine slightly decreased mRNA level. These results suggest that AT2-R expression is sensitively regulated by intracellular cation levels. The change in intracellular Na level transcriptionally regulates AT2-R expression, whereas the K blocker-dependent upregulation appears to be at least in part posttranslational. (Hypertension. 1999;33:626-632.)