Comparison of the Ability of Three Radioimmunoassay to Detect Pregnancy‐associated Glycoproteins in Bovine Plasma

Abstract

Pregnancy-associated glycoproteins (PAGs) constitute a large family of glycoproteins that are synthesized in the superficial layer of the ruminant placenta according to a spatial and temporal expression pattern. When PAGs are released in the maternal blood they can be used for pregnancy diagnosis, pregnancy follow-up and for the monitoring of the trophoblastic function. Three different radioimmunoassay systems (RIA 1, RIA 2 and RIA 3) using antisera produced against PAG I67 (RIA 1), PAG55+62 (RIA 2) and PAG55+59 (RIA 3) were used in this investigation in order to measure the PAG concentration in plasma samples withdrawn from pregnant cows and heifers during different periods following artificial insemination (AI). These systems were able to detect PAG molecules in the maternal blood as early as 21 days after AI in different concentrations (RIA 1: 0.43 +/- 0.24 ng/ml, mean +/- SD; RIA 2: 0.48 +/- 0.24 ng/ml; RIA 3: 0.64 +/- 0.37 ng/ml). On days 32 and 42 RIA 2 (4.30 +/- 1.32 ng/ml and 5.56 +/- 1.95 ng/ml) and RIA 3 (4.17 +/- 1.15 ng/ml and 5.60 +/- 1.89 ng/ml) presented significantly (p < 0.0001) higher PAG concentrations than those of RIA 1 (2.43 +/- 0.81 ng/ml and 4.01 +/- 1.48 ng/ml), respectively. After day 21, significant correlations (p < 0.0001; r >/= 0.929) were determined between the three systems. Additionally the three individual PAG profiles presented in this study showed that PAG molecules secreted in the maternal blood between 21 and 50 days after AI were better recognized by the RIA 2 and RIA 3 systems. This study clearly indicated that the ability of a RIA test to recognize PAG molecules in the maternal blood can be improved by carefully selecting the antiserum.

Isolation and characterization of eight pregnancy-associated glycoproteins present at high levels in the ovine placenta between day 60 and day 100 of gestation

“…I) to probe all fractions issued from the DEAE column, and notably used antibodies raised against caprine PAG [18]. In 2002, Perenyi et al [24] stated that RIA-2 and RIA-3 were better for detecting PAG molecules released between days 30 and 70 in pregnant cows and suggested that the antisera used in these assays (raised against caPAG55+59 and caPAG55+62) are better for detecting PAGfamily members. Using the same antisera in double radial immunodiffusion assays, we recently found them to detect more effectively than the antiserum used in RIA-1 ovine PAG present at relatively low concentration in crude sheep placental extracts [25].…”

Evaluation of false transrectal ultrasonographic pregnancy diagnoses in sheep by measuring the plasma level of pregnancy-associated glycoproteins

“…Thus the assay gave relative PAG concentrations which were used to differentiate between pregnant and non-pregnant ewes [21]. The procedures and the validation criteria of the assay were similar to those of Perényi et al [24] and are described elsewhere [21]. The cut-off value of the PAG-RIA test used to detect pregnant ewes was ≥ 1 ng·mL -1 [21].…”

Application of Radioimmunoassay for Livestock Fertility Management

“…During gestation of cow, the concentrations of PAG are detectable as early as from the 19 th to 22 nd days after the conception, to reach concentrations from 3 to 6 ng/ml in the neighborhoods of the 33 rd to 37 th days of gestation [55,56] reported that PAG concentrations increased continuously from day 20 of pregnancy until day 240 followed by a dramatic increase in the last ten days of pregnancy with maximum concentrations between day 5 and day 1 prepartum. In the bovine species, two different patterns of expression were found -those PAG that are expressed predominantly in binucleated cells (PAG 1-subgroup) are invariably absent in term placenta, whereas those PAG expressed more uniformly throughout trophoectoderm (PAG 2-subgroup) are detectable at all stages of pregnancy [57].…”