Does captopril modulate AT1 receptor gene expression in the heart and aorta of rats with RRM-induced hypertension?
AT1 receptor gene expression is regulated by different tissue-specific mechanisms in the aorta (Ang II/kinin-dependent) versus the heart (pressure-dependent) in RRM-induced hypertension.
The purpose of the present study was to test the hypothesis that hypertension induced by reduced renal mass (RRM) upregulates gene expression of the type 1 angiotensin II (Ang II) receptor (AT1) in the thoracic aorta and heart through an Ang II-dependent mechanism. Three groups of rats were given 1% NaCl water and subjected to RRM, RRM plus captopril (RRM+Cap, 30 mg/kg per day), or sham surgery. Tail-cuff systolic blood pressure was significantly elevated in RRM and RRM+Cap rats compared with sham-operated rats. The ratios of the medial wall area of the thoracic aorta and heart weight to body weight were significantly elevated in RRM and RRM+Cap rats compared with sham-operated rats. Northern blot analysis indicated that the ratio of AT1 to GAPDH mRNA in the aorta was significantly higher in RRM (1.85 +/- 0.52) compared with sham-operated (0.21 +/- 0.04) and RRM+Cap (0.55 +/- 0.20) rats. In contrast, the ratio of AT1 to GAPDH mRNA in the heart was significantly increased in both RRM (1.09 +/- 0.23) and RRM+Cap (1.00 +/- 0.09) compared with sham-operated (0.34 +/- 0.06) rats. Thus, RRM hypertension upregulates AT1 mRNA expression in both the hypertrophied aorta and heart. Captopril treatment without altering blood pressure in RRM rats prevents the increase in AT1 mRNA in the aorta but not the heart. These results suggest that different tissue-specific mechanisms of AT1 gene regulation exist; ie, in aorta, an Ang II-or kinin-dependent mechanism is operant, whereas in heart, RRM-induced upregulation of AT1 mRNA may be pressure dependent.
Wang et al. (1997) studied this question.