Immunochemical demonstration of a new pregnancy protein in the mare.

This study reports the identification of a new protein in the blood of pregnant mares which appears earlier in the gestation period than previously known markers. The researchers used techniques in immunochemistry to pick out this unique protein.

Methods

• The researchers developed an antiserum that would specifically react against serum taken from a pregnant mare. This was achieved by making the antiserum ‘ignore’ proteins found in the blood serum of stallions, allowing the antiserum to solely react with unique proteins in the pregnant mare’s blood.
• Through a technique called crossed immunoelectrophoresis, where proteins in the blood of pregnant mares (the ‘antigens’) were made to move through a gel under the influence of an electric field, the researchers could observe the newly discovered proteins as they precipitated out. There were two precipitates observed which moved at the beta-1 and alpha-2 speed ranges.

Findings

• The researchers confirmed that the protein which moved at the alpha-2 speed was the previously known pregnancy hormone, Pregnant Mare Serum Gonadotropin (PMSG).
• When they tested the absorbed antiserum in mice, it inhibited the biological effects of PMSG, supporting the conclusion that the alpha-2 mobile protein was indeed PMSG.
• The beta-1 protein, on the other hand, was a novel discovery. It was not found in the blood serum of non-pregnant mares, stallions or neutered males (geldings), confirming it to be unique to pregnant mares.
• Moreover, this protein was detected earlier in the course of pregnancy, by Day 30, whereas PMSG could only be detected by Day 42. This makes the new protein a potentially more useful early indicator of pregnancy in mares.