Studies on the regulation of granulopoiesis. II. Relationship to other differentiation pathways.

Abstract

Summary. The distribution of 59Fe in maternal, placental and foetal tissues of the rat was determined at intervals of 8, 12, 15, 17, 19, 20 and 21 days of gestation. Large amounts of 59Fe are transferred from maternal plasma to the foetuses in late gestation when foetal development is proceeding at a rapid rate. The deposition of 59Fe in the developing foetus appears governed by erythropoiesis; liver and carcass are the principal sites. 59Fe is rapidly transported across the placenta; there is no indication of a large iron pool within it. Both the allantoic and yolk sac placentae contribute significantly to placental iron uptake during the period of maximum iron transfer. Very little iron is deposited in the uterus during gestation; hence secretions from uterine glands entering the yolk sac cavity are a minor source of foetal iron. There is diminished uptake of 59Fe by the maternal liver and spleen during the period of rapid iron accumulation by the foetuses.