Contribution of fibrinogen and lipoproteins to plasma viscosity in hypercholesterolemia and hypertriglyceridemia: Evaluation by selective depletion of low-density lipoproteins or fibrinogen

Epidemiological studies suggest that the plasma fibrinogen concentration is the main determinant of plasma viscosity (PV), but the concentration of ot her macromolecules leg, immunoglobulins) and low-density lipoprotein (LDL) cholesterol and triglycerides are also correlated with PV. However, only a few data exist concerning the in vitro effects of these plasma constituents on PV. Therefore, we investigated PV before and after the specific elimina tion of fibrinogen and LDL in hypercholesterolemic and hypertriglyceridemic plasma. First, hypercholesterolemic samples (n = 7) were pumped simultaneo usly through 2 columns: a fibrinogen-depleting column containing the pentap eptide Gly-Pro-Arg-Pro-Lys (GPRPK) and a LDL-depleting column containing sp ecific antibodies against apolipoprotein B-100. In the plasma and in each f raction from the column, the cholesterol level was measured enzymatically, fibrinogen was determined by immunonephelometry, and PV was analyzed using a low-shear rotation viscosimeter. After the fibrinogen-depleting column, t he fibrinogen concentration decreased from 3.21 +/- 0.20 to 0.94 +/- 0.16 g /L (P < .005), inducing a decrease in PV from 1.27 +/- 0.02 to 1.17 +/- 0.0 1 mPas (milliPascal seconds) (P < .005). Despite a marked reduction of the LDL cholesterol after the LDL-depleting column (from 6.40 +/- 0.23 to 4.08 +/- 0.32 mmol/L,P < .005), PV remained unchanged. Second, hypertriglyceride mic samples (n = 7) were pumped through the fibrinogen-depleting column, wh ich reduced the fibrinogen concentration from 4.29 +/- 0.79 to 1.62 +/- 0.6 9 g/L (P < .001) and PV from 1.42 +/- 0.06 to 1.03 +/- 0.05 mPas (P < .01) while the triglyceride concentration remained unchanged. Our results confir m the epidemiological correlation between the fibrinogen concentration and PV in patients with hypercholesterolemia and hypertriglyceridemia. The infl uence of fibrinogen on PV seems much more pronounced than the direct effect of lipoprotein concentrations. Therefore, the elevated PV in patients with hypercholesterolemia and especially with hypertriglyceridemia seems mainly due to elevated fibrinogen levels. Copyright (C) 2000 by W.B. Saunders Com pany.