Histochemical localization of phosphatases in the pig placenta: I. Non-specific phosphatases and their relation to uteroferrin

The uterine glands, glandular secretions and areolar chorionic epithelium of the pig placenta in late gestation show high levels of histochemical phosphatase activity at acid pH, particularly towards aromatic monophosphates. The properties of this phosphatase allow its identification with the placental iron carrier protein, uteroferrin, rather than with lysosomal acid phosphatase. Alkaline phosphatase activity is restricted to the microvasculature on the maternal side of the placenta and is entirely distinct from uteroferrin phosphatase activity.