Chronic Treatment with Angiotensin II Type 1 Receptor Antagonist Suppresses Glomerular Activator Protein–1 Activity in Salt–Sensitive Hypertensive Rats

Abstract

We examined the effects of angiotensin–converting enzyme inhibitor (ACEI) and angiotensin II type 1 receptor antagonist (AT1a) on the action of protooncogene c–fos in salt–sensitive hypertensive rats. Seven–week old Dahl salt–sensitive rats fed a high (8%)–salt diet were treated with ACEI, cilazapril (10 mg/kg) or AT1a, TCV–116 (1mg/ kg) every day for 6 weeks. The control animals were fed a low (0.3%)–salt diet. Systolic blood pressure gradually increased in high–salt–loaded rats and was higher than low–salt–treated rats throughout the study. However, both medications had no significant antihypertensive effect. After 6 weeks of therapy, glomerular mRNA and nuclear protein were extracted from the resected kidneys. Competitive reverse transcription–polymerase chain reaction showed a high level of glomerular c–fos mRNA in high–salt–loaded rats and that ACEI or AT1a treatment did not significantly change its level. Electrophoretic mobility shift assay demonstrated that treatment with AT1a significantly decreased the activator protein–1 (AP–1) binding activity in the glomerular nuclear extract compared to ACEI. Our findings suggest that, compared with ACEI treatment, long–term treatment with AT1a may contribute to attenuation of the glomerular injury in salt–sensitive hypertension by inhibiting AP–1 transcription activity independent of its antihypertensive effect.