Binding of prolactin by fetal human lung cell membrane fractions.

PRL binding capacity to cell membrane fraction was studied in lung tissues obtained from 4 human fetuses or newborn infants. One of the fetuses was a stillborn delivered at 33 weeks of gestation. The newborn infants died for unknown causes within 24 h after birth. The gestational age was 20, 39 and 41 weeks. The cell membrane fraction was prepared by ultracentrifugation. Binding capacity and affinity constants were calculated according to the Scatchard method. No significant specific binding of PRL to lung tissue from the stillborn fetus was observed, while for the other 3 newborn infants the binding capacity was 5.7, 7.4 and 9.6 fmol PRL bound/mg of membrane protein, respectively. The affinity constants were in the order of 1010 M−1. These preliminary results show that human neonatal lung has receptors for PRL and suggest that PRL itself may be involved in the lung maturation.