The uteroplacental prolactin family and pregnancy.

The establishment and maintenance of pregnancy requires significant modifications of the maternal environment. During pregnancy, changes arise in virtually every major organ system within the mother, permitting growth and development of the embryo/fetus within the protected confines of the maternal reproductive tract. These gestational-dependent adaptations are believed to be controlled, at least in part, through the elaboration of chemical signals by the uterus and placenta referred to as hormones/cytokines. Some uteroplacental signals have been coupled to the regulation of specific maternal responses, while a specific function is not known for other putative signaling molecules that have been identified. The subject of this review is the uteroplacental prolactin (PRL) family. PRL is a multifunctional hormone/cytokine that has been used as an evolutionary template for the generation of regulatory molecules involved in the establishment and maintenance of pregnancy. Several reviews on the PRL family have appeared over the past several years and are recommended [1-7].