[Effect of platelet concentrate transfusions on the thrombopoietic activity in rats]

Rats were given selected doses of rabbit antiplatelet serum (APS) inducing after 6 hours thrombocytopenia at the level of 14% of the initial platelet count followed by a gradual rise in this count (after 12, 24 and 48 hours). Eight hours after APS administration the rats were given transfusion of a concentrate containing 1-2 X 10(9) fresh allogenic platelets (group A) or the same number of previously frozen platelets (group B). Rats receiving no concentrate after APS administration (group C) and rats receiving neither APS nor concentrate (group D) served as controls. Using a bioassay on mice the serum thrombocytopoietic activity (ATS) was determined in the rats and the platelet count was measured by the direct method. These determinations were done before and 24 and 48 hours after the experiment. It was shown that after 24 hours the values of the platelets (p less than 0.1) and ATS (p less than 0.001) were lower in group B than in the remaining groups. This suggests an inhibitory effect of the frozen concentrate on the ATS. After 24 hours the platelet count was highest in group A, and after 48 hours in group C, which suggests that transfusion of fresh concentrate has an immediate effect but in a later phase it inhibits spontaneous mechanisms effacing the thrombocytopenic effect.