Haemorheological effects of losartan and enalapril in patients with renal parenchymal disease and hypertension

The objective of this study was to compare the effects of the angiotensin I I (ang II) antagonist, losartan and the angiotensin-converting enzyme inhib itor (ACEI), enalapril on haemorheology. Twenty-nine patients with renal pa renchymal disease and hypertension were enrolled in the prospective, open, parallel study that involved a 14-day washout period followed by a 120-day treatment period. Patients were allocated randomly to receive either losart an 50-100 mg/day (n = 15) or enalapril 2.5-10 mg/day (n = 14) to achieve bl ood pressure control <140/90 mm Hg. Blood pressure, haemorheology profile a nd plasma fibrinogen concentration were measured after the washout phase an d after 2, 10, 60, and 120 days of treatment. The data were analysed using ANOVA with repeated measures. Twenty-seven patients completed the study. Tr eatment with both losartan and enalapril was associated with a significant decrease (P < 0.05) in relative high shear rate whole blood viscosity, indi cating an increase in blood cell deformability. In patients taking losartan , the increase in blood cell deformability did not result in a decrease in mean whole blood viscosity due to a concomitant, significant increase in me an plasma viscosity (P < 0.01). In contrast, the improved cell deformabilit y in patients treated with enalapril resulted in a small and statistically insignificant decrease in mean whole blood viscosity (P = 0.06; mean change = -0.15 mPa sec). The mechanism of the increase in blood cell deformabilit y and the rise in plasma viscosity associated with losartan remain unclear. It is possible but unproven that the improvement in intrinsic blood cell r heology with losartan and enalapril may be the result of changes in cation transport systems and/or the consequence of the protective antioxidant prop erties of drug metabolites.