Protein synthesis and secretion by the human endometrium and decidua during early pregnancy

To investigate the role of the endometrium in sustaining early pregnancy, specimens of endometrium from early pregnancy were incubated in vitro with radiolabelled amino acids, and protein synthesis and secretion were studied by subsequent fluorographic analysis of one-and two-dimensional polyacrylamide gels. Seventeen secreted endometrial proteins (EP) were identified. Changes were demonstrated in the rate of synthesis and/or secretion of a number of these proteins during early pregnancy. Two proteins, EP 14 and EP 15, are the principal secretory proteins of pregnancy endometrium. EP 14 (subunit mol. wt 32 000) is associated with decidualized endometrium and its rate of synthesis/secretion increases during early pregnancy. EP 15 (subunit mol. wt 28 000) is also synthesized and secreted by the secretory endometrium during the menstrual cycle, and during early pregnancy, but its secretion declines to undetectable levels by week 15-16. These proteins may provide useful markers of endometrial function and differentiation during the menstrual cycle and pregnancy.