Serological detection of early pregnancy in cattle and partial characterization of a serum glycoprotein associated with early pregnancy.

Sera from heifers prior to artificial insemination (AI), 1-8 days after AI, and 7 days after embryo removal were investigated by crossed immunoelectrophoresis (CIE) by use of rabbit antiserum produced against bovine early pregnancy serum and intensively absorbed with non-pregnancy serum. One precipitation peak appeared in the alpha-globulin region when sera of non-pregnant heifers were under study. An additional peak could be demonstrated in the same region when sera of early pregnant heifers were investigated. By this method 91.5% of 71 sera samples were classified correctly to be pregnant or non-pregnant. The glycoprotein character of the above two serum components could be shown by binding to concanavalin A (Con A) in lectin affinity CIE. Relative molecular weights were estimated to be about 70,000 and 80,000 for the peptides of these two proteins applying sodium dodecyl sulfate polyacrylamide gel electrophoresis of precipitates cut out from CIE-plates. As shown previously close relation of this early pregnancy associated protein (EPAP) to the early pregnancy factor is supposed because of its characteristics and its ability to affect cellular immunity.