Abstract 349 Poster Session I, Saturday, 5/1 (poster 133)

The prolactin (PRL) family is comprised of a group of hormones/cytokines that are expressed in the anterior pituitary, uterus, and placenta. These proteins are hypothesized to control maternal-fetal adaptations to pregnancy. In this report, we have identified rat homologues for two known nonclassical members of the mouse PRL family, proliferin-related protein (PLF-RP) and PRL-like protein-F (PLP-F). We present data on their cDNAs, describe their expression patterns, as well as their intraplacental cellular sites of synthesis. Perusal of the NCBI dbEST database resulted in the identification of putative rat PLF-RP and PLP-F cDNAs. The cDNAs were obtained from the IMAGE consortium and Research Genetics, sequenced, and their corresponding mRNAs characterized. Overall, rat PLF-RP and PLP-F showed considerable structural similarities with mouse PLF-RP and PLP-F; 84% and 79% nucleotide identity, respectively. However, most interestingly the sites of PLF-RP and PLP-F differed in the rat versus the mouse. PLF-RP was dually expressed in trophoblast giant cell and spongiotrophoblast layers of the junctional zone of the mouse chorioallantoic placenta, whereas in the rat, PLF-RP was expressed exclusively in the labyrinth zone of the chorioallantoic placenta. In the mouse, PLP-F is an exclusive product of the spongiotrophoblast layer, whereas in the rat, trophoblast giant cells were found to be the major source of PLP-F, with only a minor contribution from spongiotrophoblast cells late in gestation. PLF-RP possesses anti-angiogenic actions and its expression in labyrinthine trophoblast suggests a potential role in limiting vascular development at the primary transport barrier between maternal and fetal blood supplies. Although, the biological actions of PLP-F are yet to be determined, its expression pattern at the maternal interface from early to late gestation indicates functions associated with maternal adaptations to pregnancy. In summary, we have established the presence of PLF-RP and PLP-F in the rat. The findings expand our knowledge of these two cytokines/hormones and provide additional strategies for studying their function.

Supported by HD 20676 and HD 29797