Ontogeny of prolactin recep¬ tors in rat decidual tissue: binding by a locally produced pro¬ lactin-like hormone. Journal ofEndocrinology

The objectives of this investigation were to determine whether decidual tissue possesses specific binding sites for prolactin, and to examine whether the locally pro-duced prolactin-like hormone binds to these recep-tors. Characterization of the binding of prolactin to decidual tissue from rats at day 9 of pseudo-pregnancy revealed specific, high-affinity sites. Binding approached saturation with increasing concentrations of either the ligand or the protein. Cytosolic extracts of day-9 decidual tissue, containing various amounts of decidual luteotrophin which possesses several of the physiological and biochemical characteristics of prolactin, displaced the binding of 125I-labelled pro-lactin to decidual membranes in a linear fashion. Prolactin-binding sites were detectable 72 h after induction of decidualization and 48 h after the appearance of decidual luteotrophin in the decidua. Prolactin receptor concentrations increased signifi-cantly between days 8 and 9, reached a plateau between days 9 and 12 and declined abruptly on days 14 and 15, accompanied by a similar decline in deci-dual luteotrophin concentration in the tissue. Thus rat decidual tissue possesses specific receptors for prolac-tin to which decidual luteotrophin locally produced can bind, thereby suggesting an auto/paracrine role for this substance. J. Endocr. (1986) 110,115\p=n-\12