Reduction of resistance artery stiffness by treatment with the AT1-receptor antagonist losartan in essential hypertension

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Abstract
In spontaneously hypertensive rats resistance artery structure, endothelial dysfunction and geometry-independent wall stiffness were reduced by an angiotensin AT1-receptor antagonist. In previous studies of human hypertension, interruption of the renin-angiotensin system corrected small artery structure and endothelial dysfunction, whereas the β-blocker atenolol did not. We hypothesized that the AT1R antagonist losartan, but not the β-blocker atenolol, would reduce stiffness of gluteal subcutaneous small arteries in essential hypertensive patients. Seventeen untreated mild essential hypertensive patients (47±2years; 75% male) were randomly assigned in double-blind fashion to losartan or atenolol treatment for one year. Small, resistance size arteries were studied on pressurized myographs. Blood pressure (mmHg) was reduced (p<0.01) from 145±4/101±2 and 147±6/98±2 to 128±4/86±2 and 131±3/84±1 by losartan and atenolol, respectively.The media/lumen ratio of small arteries was unaffected by atenolol (8.3±0.3% before and 8.8±0.5% after treatment). In contrast, losartan reduced media/lumen ratio from 8.4±0.4% to 6.7±0.3% (p<0.01). Whereas isobaric elastic modulus was unaffected by either treatment, geometry-independent stiffness (slope of elastic modulus vs. stress) was reduced from 9.7±1.2 to 6.1±0.9 (P<0.05) under losartan treatment, but was unchanged by atenolol (8.2±1.3 to 7.8±0.6). In conclusion, treatment with losartan reduced stiffness and structural alterations of subcutaneous resistance arteries of previously untreated essential hypertensive patients, whereas atenolol failed to do so.