A study of megakaryocytes in albino rats.

Abstract

Liver, spleen, and bone marrow from albino rats varying in age from 20 days gestation to 120 days old were studied to determine sites of formation of megakaryocytes. By counting 30 high-power microscope fields it was found that the liver was the major site of megakaryocytopoiesis in fetal animals. While megakaryocytes could be found in the red pulp of fetal spleens late in development, this organ did not supersede the liver in megakaryocytopoiesis until a few days after birth. Similarly, in rats 10 days old megakaryocytes could be found in the developing bone marrow of the femur. The bone marrow does not become a significant site of megakaryocytopoiesis until about 40 days after birth when cell counts in the vicinity of 700 megakaryocytes per 30 high-power fields are attained.The number of megakaryocyte mitoses occurring in liver and spleen exceeded that in bone marrow by a figure inversely proportional to the total number of megakaryocytes counted in the liver and spleen. Mitoses found in megakaryoblasts are thus concluded to be endoploid in nature, carried over as an epiphenomenon from the immediate megakaryoblast precursor cell.Possible phagocytosis occurring in megakaryocytes of liver and splenic red pulp of young rats was studied.