Alteration of rat bone marrow megakaryocytes following administration of cytosine arabinoside, daunomycin and hydroxyurea.

The in vivo effects of three cytotoxic agents--cytosine arabinoside, daunomycin and hydroxyurea on rat bone marrow megakaryocytes were studied, specifically the relative count, the type percentage and the morphology. All three agents caused thrombo-cytopenia, a decrease in the number of megakaryocytes relative to the nucleated bone marrow cells, and a decrease in the percentage of megakaryoblasts, associated with an increase in the percentage of granular megakaryocytes. A decreased lobulation of the megakaryocytes was observed following the administration of cytosine arabinoside and of daunomycin. Thrombosthenin, examined immunologically, remained detectable in the bone marrow smears throughout the various stages of megakaryocyte alteration.