Altered rheological properties of red and white cells during normal gestation

Abstract

Beside plasma viscosity and the functional state of the vessel wall, placental perfusion is determined by the concentration and behaviour of the blood cells. In order to evaluate the contribution of erythrocytes to placental flow in late pregnancy, we applied a new filtration technique allowing to analyze the passages of erythrocytes through a single pore. As a parameter of decreased deformability in late pregnancy, we found a significant increase in transit time (22.69 +/1.60 ms vs 24.03 +/2.40 ms; pore size 4.1 pm; hydrostatic pressure 100 Pa) correlating with the mean cell volume (r=0.763). Due to their size and rigidity, their property to adhere to altered endothelium and to release radicals and mediators, granulocytes were the second point of interest to investigate in late pregnancy. Granulocytes were more adherent in vitro when stimulated with PMA, FMLP or in the absence of these mediators. This was shown for BSAand fibronectincoated wells (BSA: PMA 72.6% vs 67.2%, FMLP 43.4% vs 36.1%, unstimulated 26.5% vs 15.4%; fibronectin: PMA 71.6% vs 66.7%, FMLP 44.7% vs 31.1 %, unstimulated 25.7% vs 18.2%). Transit times of granulocytes through 8 pm pores were significantly shorter in the pregnant group at 400 Pa (5.02 +/0.50 ms vs 5.49 +/0.74 ms), nearly identical at 200 Pa (9.34 +/1.79 ms vs 9.57 +/1.65 ms) and impossible to measure at 100 Pa (frequent obstruction). Luminol-enhanced whole blood chemiluminescence of unstimulated granulocytes was decreased in the pregnant group (0.19 counts/ce11l2s vs 0.33 counts/cell12s) but exceeded values of the control group when stimulated with PMA or FMLP (PMA: 20.13 counts/cell/2s vs 15.90 counts/cell/2s; FMLP: 2.35 counts/cell/2s vs 1.94 counts/cell/2s). Our results may indicate that in times of insufficient placental flow, as it is seen in hypertension-related gestational disorders, a decreased erythrocyte deformability as well as an enhanced adhesivity and chemiluminescence of activated granulocytes may perpetuate and aggravate placental malperfusion.