Effect of platelet homogenate on platelet production of bone-marrow-transplanted mice.

Haemopoiesis of mice was reconstituted with 1 X 10(6) bone marrow cells after 800 r total body irradiation. Then their megakaryocytopoiesis was inhibited by platelet homogenates given at different points of time on three subsequent days. The effect was measured by the peripheral platelet counts on the 14th day after transplantation when the platelet count of irradiated and marrow-transplanted CFLP animals was 410 X 10(9)/l, and that of CBA mice was 185 X 10(9)/1. Platelet homogenates prepared from 1-2.5 X 10(8) platelets daily given on days 1, 2 and 3 did not significantly reduce the peripheral platelet count estimated on the 14th day, while homogenates given on days 8, 9 and 10 reduced it markedly. Homogenates prepared from 0.7-1.0 X 10(6) white blood cells did not influence the 14th day platelet count. Thus, platelet homogenates exert their inhibitory effect at a late stage of platelet production, i.e. not by an inhibition of thrombopoietin or a thrombopoietin effect.