Secretory profiles of pregnancy-associated glycoproteins at different stages of pregnancy in the goat

Abstract

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.