Secretory Profiles of Pregnancy-Associated Glycoproteins at Different Stages of Pregnancy in the Goat

Plasma concentrations of pregnancy‐associated glycoproteins (PAG) were determined in goats during pregnancy by two homologous radioimmunoassays that employed caprine PAG₅₅₊₆₂ (caPAG₅₅₊₆₂) and caprine PAG₅₅₊₅₉ (caPAG₅₅₊₅₉) and their specific antisera. The effects of fetal number on PAG concentrations were analysed. The concentrations of caPAG₅₅₊₆₂ were higher than that of caPAG₅₅₊₅₉ throughout pregnancy (p <0.05). Both caPAG₅₅₊₆₂ and caPAG₅₅₊₅₉ reached maximal levels in week 8 (48.6 ± 5.0 and 30.4 ± 4.3 ng/ml, respectively), decreased between weeks 12 and 14 (45.5 ± 2.5 to 31.9 ± 2.7 ng/ml and 30.6 ± 2.1 to 15.8 ± 2.8 ng/ml, respectively, p <0.01) and remained relatively constant until parturition. Twin‐bearing goats had higher PAG concentrations than single‐bearing animals, but the difference was only significant in week 4 (52.3 ± 3.7 versus 30.9 ± 3.9 ng/ml and 18.9 ± 1.7 versus 12.6 ± 2.0 ng/ml, for caPAG₅₅₊₆₂ and caPAG₅₅₊₅₉, respectively, p <.,0.05). This is the first study of PAG concentrations in goat throughout pregnancy by a homologous radioimmunoassay system. The profiles of caPAG₅₅₊₆₂ and caPAG₅₅₊₅₉ were closely parallel. Concentrations of PAG were lower than those obtained by a heterologous radioimmunoassay and their patterns were also different, due to a different specificity of the antisera used in heterologous system. Goats that delivered twins had higher PAG concentrations at the time of implantation than those that delivered a single fetus, indicating that PAG concentrations provide a useful measure of the trophoblast secretory activity.