[The effect of aspirin on rheological properties of erythrocytes in essential hypertension].

Essential hypertension is one of the most important risk factors for cardiovascular diseases. Its pathophysiological mechanism is unknown. Recent data suggests that deformability and aggregation of red blood cells may play an important role in the regulation of blood rheology in hypertension. Simultaneously there are reports suggesting that antihypertensive effects of angiotensin converting enzyme inhibitors (ACEI) could be counteracted by high doses of aspirin. We postulate that these effects could be related to the changes in blood rheology. Accordingly we designed a study to evaluate the effect of low or high dose of aspirin on deformability and aggregability of red blood cells from patients with essential hypertension. Deformability and aggregability of red blood cells were measured by laser diffractometer (Rheodyn SSD, Myrenne GmbH) and computerized automatic aggregometer (MA1 Myrenne GmbH, Germany), respectively. The effects of aspirin on deformability and aggregation of red blood cells were studied ex vivo in whole blood from three groups of patients with essential hypertension (group I: 10 patients receiving placebo, group II: 23 patients receiving 75 mg/day p.o. aspirin for 3 days, and group III: 23 patients receiving 300 mg/day p.o. aspirin for 3 days). Subjects in all groups received the same combination of antihypertensive agents consisting of: one of ACEI (enalapril or perindopril), one of beta-antagonists (metoprolol or bisoprolol), and diuretic agent (indapamid). In patients receiving high dose of aspirin (300 mg/day) we observed that erythrocyte aggregability was 25% higher than in the placebo group (MEA = 25.8 +/- 6 SD, vs MEA = 20.6 +/- 3 SD, p < 0.05). Aspirin had no effects on deformability of erythrocytes or on arterial blood pressure. High doses of aspirin or possibly also other nonsteroidal anti-inflammatory drugs (NSAID) in patients receiving antihypertensive therapy can directly affect rheological properties of the blood due to the activation of red blood cell aggregation. Increased aggregation of red blood cells during antihypertensive therapy may be an important indicator of the worsening of organ perfusion.