RED-BLOOD-CELL AGGREGATION AND MICROCIRCULATION IN RAT CREMASTER MUSCLE

Using intravital microscopy of the rat cremaster muscle, we studied th e effects of changing red blood cell (RBC) aggregation on RBC arteriol ar velocity and perfused capillary density (PCD). To modify RBC aggreg ation, 2 and/or 10% dextran (molecular weights 40,000, 70,000 or 480,0 00) or fresh rat plasma was infused into adult male rats via a normovo lemic hemodilution procedure. The high-molecular-weight dextrans (70,0 00 and 480,000) both induced RBC hyperaggregation associated with simi lar dose-dependent decreases in RBC arteriolar velocity (30 and 40% fo r dextran concentrations of 2 and 10%, respectively) and in PCD (35 an d 37%, respectively, for the two concentrations). Conversely, with 40, 000 molecular weight dextran or plasma, we observed a 30% increase in RBC arteriolar velocity, but no change in PCD or hyperaggregation. Int ravenous injection of the antiaggregating drug troxerutin (10(-3) M), either before or after 2% dextran 70,000, significantly inhibited the effects of this dextran on RBC arteriolar velocity and on PCD. We conc lude that RBC hyperaggregation can lead to changes in both arteriolar velocity and PCD and may, therefore, impair tissue oxygenation.