CHARACTERIZATION OF PLATELET ABNORMALITIES OF TESTER-MORIYAMA (TM) RATS WITH STORAGE POOL DEFICIENCY

Platelet abnormalities of Tester Moriyama (TM) rats, which have prolon ged bleeding time with normal platelet count, were characterized by co mparison with those of fawn-hooded (FH) rats with platelet storage poo l deficiency (SPD), Morphologically, the dense granules were virtually lacking in platelets from TM and FH rats, Platelets from TM and FH ra ts aggregated in response to adenosine diphosphate (ADP), but failed t o have secondary aggregation. In contrast, platelet aggregation was co mpletely absent in response to 1 to 20 mu g of collagen/ml, although p artial aggregation was observed at the higher dosage of 50 mu g/ml. No rmal amounts of platelet membrane glycoproteins IIb/IIIa were expresse d in TM and FH rats, but platelet adenosine triphosphate (ATP) and ADP contents were lower than those in platelets from control Wistar rats, Platelet ATP-to-ADP ratio of TM and FH rats was significantly higher than that of Wistar rats, Serotonin content in platelets from TM and F H rats was 20 to 25% that of Wistar rat platelets. These results sugge sted that platelet abnormalities of TM rats are a typical characterist ic of platelet SPD and are similar to those of FH rats, which are gene tically different from TM rats, Therefore, TM rats may serve as a usef ul animal model for the study of platelet SPD.