Intravital-microscopic observations on the intravascular behavior of blood cell components during dietary-induced hyperlipidemia in the male rabbit

Reperfusion-induced changes in capillary perfusion and filtration: effects of hypercholesterolemia

Fluid filtration rate (J(v)/S) and red blood cell velocity (V(RBC)) in individual mesenteric capillaries of normocholesterolemic (NC) and hypercholesterolemic (HC) rats were measured before and after ischemia and reperfusion (I/R). In NC rats, a correlation was found between baseline J(v)/S and the percent of the feeding arteriole length that was paired (<15 micrometer) with a postcapillary venule (A-V pairing), but not in the HC group. Additionally, in NC rats only, a correlation was found between baseline V(RBC) and A-V pairing. In capillaries in which A-V pairing was substantial (>20%), V(RBC) dropped after reperfusion in the HC group (54% of baseline; P < 0.05), but not in the NC group (79%). The decrease in V(RBC) in HC rats could be attenuated by a P-selectin antibody (PB1.3). PB1.3 was also able to attenuate the increase in I/R-induced capillary J(v)/S in HC rats (median increase = 1.26-fold vs. 1.53-fold without PB1.3). These data suggest a role for A-V pairing in capillary perfusion in NC rats and a potential role for P-selectin in I/R-induced microvascular dysfunction in HC rats.

Effect of beraprost, a stable prostacyclin analogue, on red blood cell deformability impairment in the presence of hypercholesterolemia in rabbits

We evaluated the effects of orally administered beraprost, a stable prostacyclin analogue, on the rheological behavior of red blood cells (RBC) in the presence of hypercholesterolemia. Rabbits fed a cholesterolrich diet were administered various doses of beraprost or pravastatin. We evaluated rheological behavior of RBC by assessing RBC deformability, using a positive-pressure filtration method. The maximum pressure generated by passing a suspension of RBC through a membrane filter was used as an index of RBC deformability. After animals were fed cholesterol for 16 weeks, the maximum pressure increased significantly from 172 +/- 15 mm Hg at baseline to 261 +/- 18 mm Hg (p < 0.01, n = 24). The reduction in RBC deformability associated with hypercholesterolemia improved dose dependently during 1-h incubation with various doses of beraprost. In ex vivo study, beraprost markedly restored RBC deformability 3 h after its oral administration to 218 +/- 17 mm Hg (n = 9) at a low dose and to 215 +/- 20 mm Hg (n = 9) at a high dose. The effect persisted for at least 2 h. Pravastatin failed to reduce the increased maximum pressure. Findings suggest that beraprost treatment may improve the microcirculation by restoring RBC deformability in the presence of hypercholesterolemia.

The antioxidant butylated hydroxytoluene prevents early cholesterol-induced microcirculatory changes in rabbits

Microcirculation was studied during 10 wk in untreated rabbits (n = 13) and in rabbits treated with dietary addition of 1% cholesterol (n = 13), 1% cholesterol + 1% of the antioxidant BHT (butylated hydroxytoluene) (n = 11), or 1% BHT (n = 5). The studies were performed by direct intravital microscopic imaging of the left and right conjunctivae with the use of a stereo microscope and a high resolution television camera. Microvessel diameter, erythrocyte flow velocity, and microhemorheologic conditions were evaluated quantitatively via a computer-assisted digital image processing system. Significant and marked changes occurred in all the above variables as a consequence of cholesterol feeding. After 3 wk of feeding there was a dramatic decrease (approximately 30%) in blood flow velocity in arterioli of the third order (P < 0.0001), accompanied by aggregation of cells in 40-50% of the smaller conjunctival vessels (P < 0.0001). These changes were enhanced further during the following 7 wk of treatment. All the above changes in the microcirculation were markedly reduced by the addition of BHT treatment. The diameter of the above arterioli decreased in the purely cholesterol-fed group (P < 0.005), whereas this did not occur in the group fed both cholesterol and BHT. In rabbits fed BHT in the absence of cholesterol, there was no significant effect on any assessed microcirculatory variable. In conclusion, the results demonstrate that the antioxidant BHT prevented early cholesterol-induced microcirculatory changes. This prevention occurred in the absence of a reduction of blood lipid levels. The results provide strong support for the hypothesis that a considerable part of the effects on microcirculation in hypercholesterolemia may be due to cholesterol-induced oxidations and not to cholesterol itself. The results are discussed in relation to the previously demonstrated antiatherogenic effect of BHT and the possible use of antioxidants in the therapy and prophylaxis of atherosclerosis.

Participation of serum albumin and LDL-cholesterol in impaired blood cell-filterability affected by white blood cells in patients with cerebral thrombosis

We examined the effect of white blood cells (WBCs) on the red blood cell (RBC)-filterability, and the influence of plasma components on their interaction of their microcirculatory behaviour in cerebral thrombosis patients. Subjects studied were 20 patients with a history of cerebral thrombosis (60 +/- 4.7 years old) (mean +/- SD) and 28 healthy controls (59 +/- 5.4 years old). Filterability indices of RBC suspension (RFI) and suspension with RBCs plus WBCs (RWFI) were measured by the method of Nuclepore filtration. The values of RFI in patients and controls were 0.44 +/- 0.12 and 0.56 +/- 0.16 ml min-1 (mean +/- SD), and RWFIs were 0.33 +/- 0.092 and 0.40 +/- 0.11 ml min-1, respectively. The differences in both of these values between patients and controls were significant (p < or = 0.01 for RFI and p < or = 0.05 for RWFI, based on Student's t test, respectively). Both RFI and RWFI in bed-ridden patients were lower than those in the more active counterparts (p < or = 0.05, based on Student's t test). In patients, RFI and RWFI correlated positively with serum albumin (r = +0.515, p < 0.05; r = +0.533, p < 0.05, based on Student's t test, respectively). The net lowering effect of WBCs on RFI (RFI-RWFI) correlated positively with serum LDL-cholesterol in patients (r = +0.574, p < 0.01, based on Student's t test). WBCs play a significant role in reducing RFI, and its effect is related to the pathemas of patients.(ABSTRACT TRUNCATED AT 250 WORDS)