EFFECTS OF LOSARTAN ON CEREBRAL AND OCULAR CIRCULATION IN HEALTHY-SUBJECTS

Aims The introduction of specific inhibitors of AT(1) receptors, such as losartan, has enabled the investigation of the renin-angiotensin-sy stem (RAS) in humans in vivo. We studied the role of the RAS in the ce rebral and ocular circulation in healthy subjects. Haemodynamic effect s of orally administered losartan were investigated with non-invasive methods. Methods In a placebo-controlled randomized, double-blind two way crossover design losartan (100 mg orally) or placebo was administe red in 10 healthy subjects. The effect of losartan was studied at hour ly intervals for 8 h. In addition, the effect of losartan on haemodyna mic changes induced by exogenous angiotensin II (Ang II) was assessed. Blood flow velocities in the ophthalmic and the middle cerebral arter y (OA, MCA) were measured with Doppler sonography. Pulsatile choroidal blood flow was estimated with laser interferometric measurement of fu ndus pulsation. Results Losartan significantly increased fundus pulsat ion amplitude (+11%, 95% CI: 5 to 16% P < 0.0001), tended to increase resistive index in the ophthalmic artery (+12%, 95% CI: 0 to 23%) and tended to decrease mean arterial pressure (-15%, 95% CI: -23 to -1%). Ang II induced effects on cerebral, ocular and systemic haemodynamics were prevented by preceding administration of losartan. Conclusions Th e present data suggest that Ang II is not a major determinant of cereb ral and ocular blood flow in vivo. The observed changes in cerebral an d ocular haemodynamic parameters after losartan administration reflect effects on systemic blood pressure.