Increase in red blood cell aggregability following experimental occlusion of the middle cerebral artery in cats

Red blood cell (RBC) aggregability has been reported to be enhanced in patients with ischemic cerebrovascular disorders. We investigated whether the ischemic insult per se causes such enhancement of RBC aggregability. Fifteen cats were anesthetized and the middle cerebral artery (MCA) was occluded. Successful occlusion was confirmed from a sudden decrease in cerebral blood volume. Venous blood samples (2 ml) were obtained from the femoral vein before and after MCA occlusion. The blood was immediately mixed with disodium EDTA (2 mg), and the RBC aggregation rate (RBC-A) was measured employing a whole-blood RBC aggregometer. The control value for RBC-A was 0.213 +/- 0.007/s (mean +/- SEM). RBC-A was already increased at 1 h after the occlusion (0.229 +/- 0.007/s, p less than 0.01) and maintained a significantly high level until 2 h after the occlusion (0.229 +/- 0.018/s, p less than 0.05) as compared with the control value. These results suggest that a brief insult of cerebral ischemia brought about an enhancement of the RBC aggregability in the circulating blood.