Placental proteins in ruminants: biochemical, physiological and zootechnical aspects

During the last decade, investigations were carried out by several research groups in order to characterize proteins or glycoproteins synthesized in the ruminant placenta. Recently, as results of this research, a large family of pregnancy-associated glycoproteins (PAGs) was discovered. Using molecular biology techniques, they were found to be members of the superfamily of the aspartic proteinases which also contains pepsinogen, chymosin, renin, beta-secretase, cathepsin D and E etc. Synthesized in the mono and/or binucleate cells of the trophoblast, some forms of PAG seem to lack of proteinase activity. It is likely they are synthesized together with molecules involved in the tissue remodeling of the placenta. Their release in large quantities into the maternal blood circulation results in measurable plasma concentrations.
Thanks to international collaborative studies, we have shown that PAG levels are a good indicator of feto-placental well-being and that sharp decreases in PAG levels occur just before pregnancy failure in cows and in goats. In some countries, the PAG assay is available for veterinarians in the regional laboratories responsible for animal health including immunodiagnosis for brucellosis, IBR, BVD, CAEV, VISNA-MEDI etc.