Role of erythropoietin and placental lactogen in the control of erythropoiesis during pregnancy.

Abstract

As pregnancy progressed in the mouse, the time required to clear radioiron from the plasma decreased; incorporation of radioiron into erythrocytes and the 24-h plasma iron turnover rate (PITR) increased. Exposure of pregnant mice to hyperoxia, to suppress endogenous erythropoietin, markedly prolonged the time required for clearance of 50% of the injected radioiron from the plasma [Formula: see text], but this time was significantly faster than that observed in normal mice so exposed. Placental lactogen, which had previously been shown to augment erythropoietin, increased the plasma iron [Formula: see text] clearance time and the incorporation of radioiron into erythrocytes. In pseudopregnant mice, where there is a physiologically balanced ratio of hormones necessary for the maintenance of pregnancy, in the absence of increased erythropoietin the [Formula: see text] and incorporation of radioiron into erythrocytes were normal. The data suggest that during pregnancy the major factor controlling erythropoiesis is erythropoietin. The inhibitory effect of increased concentrations of estrogens during pregnancy is balanced by an increased production of erythropoietin and the presence of such ancillary hormones as placental lactogen. The latter hormone, with erythropoietin, may be responsible for the increased red cell mass during pregnancy.