Synthesis and release of polypeptides by the baboon (Papio anubis) uterine endometrium in culture

This study was designed to identify proteins released in culture by the baboon uterine endometrium. Endometrial tissues from cyclic baboons were minced and cultured in the presence of L-[3H]leucine or L-[35S]methionine for 24 h. The culture media and solubilized tissues were analyzed by one- and two-dimensional gel electrophoresis for secretory products that were uterine-specific. The fluorographs of the one- and two-dimensional gels demonstrated that the proteins released into culture media could be divided into two groups. Group I proteins were present throughout the menstrual cycle and showed minor cyclic variations in intensity, and Group II proteins were those that appeared to be hormonally modulated. Group I was comprised of several high molecular weight proteins (Mr greater than 200,000) and at least five additional proteins ranging in molecular weight from 80,000 to 37,000, with isoelectric points (pIs) of 5.1 to 6.0. Group II consisted of a protein (Mr 33,000; pI 7.6) that was observed only during the follicular stages of the cycle and two other groups of proteins (Mr 130,000 and 88,000) that were present during the luteal stage. Western blots of tissue culture media incubated with antibodies against human placental proteins (PP) and prolactin demonstrated that PP4 and PP7 were secreted throughout the cycle while PP12, PP16, and prolactin were only present during the luteal stage of the cycle. Thus, it appears that the baboon uterine endometrium, like that of the human, secretes a wide array of proteins in culture. Our results also suggest that a few of these proteins are immunologically similar. Endometrial differentiation during the menstrual cycle altered the secretion of some proteins, whereas the synthesis of others appeared to be dependent on either estrogen or progesterone and were stage-specific.