Effects of pregnancy on erythropoiesis in the splenic red pulp of the mouse: A quantitative electron microscopic study.

Abstract

The effects of pregnancy on erythropoiesis in the splenic red pulp of the mouse was examined quantitatively by EM. In the red pulp of a normal female at 60 days of age, erythroid cells were most numerous, constituting 73.3% of all the hemopoietic cells; 55.1% of the erythroids were erythroblasts. By quantitative stereology, erythroblasts could be classified by nuclear size into 3 classes: small, medium and large. Out of all the erythroblasts small erythroblasts constituted 50%, medium erythroblasts 35% and large erythroblasts 15%. The relation of the nuclear volume of large, medium and small erythroblasts was approximately 4:2:1. In pregnancy erythroids, particularly erythroblasts, increase markedly in number. The estimated total number of erythroblasts in the red pulp was 3.8 .times. 107 for the normal, 9.7 .times. 107 at 5 days of pregnancy, and 17.4 .times. 107 at 15 days. In early pregnancy, large and medium erythroblasts increased more markedly than small ones, while in late pregnancy not only large and medium but also small erythroblasts were much increased in number. At 20 days postpartum, erythroblasts had returned to normal in number and proportion of each class. The quantitative stereological approach proved to be useful for assessing erythropoietic activity in the splenic red pulp.