Detection and synthesis of a progestagen-dependent protein in human endometrium

Abstract

Immunological and biochemical methods were employed to demonstrate the presence of progestogen-dependent proteins in human endometrium. Cytosols were prepared from proliferative and secretory phase endometria of cycling women, from decidua and decidua-rich tissues of women in early pregnancy and from decidua of tubal pregnancy. Antisera were raised in rabbits against the antigens of decidua of tubal pregnancy and decidua-rich tissues. Immunoelectrophoresis, Ouchterlony''s immunodiffusion test and polyacrylamide gel electrophoresis using native gels revealed 2 antigenic proteins, designated antigens A and B, in secretory endometria, decidua-rich tissues, decidua and in decidua of tubal pregnancy. Only 1 antigenic protein was detected by sodium dodecyl sulfate-gel electrophoresis: antigens A and B may therefore be 2 different proteins or 2 forms of a single protein. The antigens could not be detected in non-pregnancy sera or in term placentae. Double isotopic labeling (incubation of tissues with [3H]- and [14C]leucine) followed by protein fractionation methods were used to compare the in vitro synthesis rates of antigens in proliferative tissues with those in decidua or secretory endometria. The rate of synthesis of antigens A and B was markedly higher in the decidua and secretory endometria than in the proliferative endometria. During progestogen-dependent transformation of proliferative phase endometria into secretory endometria and decidua in women, there apparently is a selective stimulation of at least 1 species of pregnancy-associated protein.