Radioimmunoassay of a Bovine Pregnancy-Associated Glycoprotein in Serum: Its Application for Pregnancy Diagnosis1

Abstract

A sensitive and specific double-antibody RIA for a bovine pregnancy-associated glycoprotein (bPAG) is described. The limit of detection was 0.2 ng/ml. The assay was specific for bPAG in that pituitary and placental gonadotropic hormones and other placental or serum proteins assayed in serial dilutions did not cross-react. The RIA allowed measurement of bPAG in placental extracts, fetal serum, fetal fluids, and serum or plasma of pregnant cows. About 20% of unbred heifers and nonpregnant cows had detectable levels ranging from 0.30 +/- 0.09 to 0.50 +/- 0.17 ng/ml (mean +/- SD), and 15% of bull sera showed higher concentrations (3.01 +/- 1.73 ng/ml) of bPAG or bPAG-like protein. Variations among animals was observed in fetal serum bPAG concentrations. Bovine PAG was detected in maternal peripheral blood at Day 22 of pregnancy (mean +/- SD, 0.38 +/- 0.13 ng/ml) in some animals and at Day 30 in all pregnant cows. Peripheral serum bPAG levels increased progressively to 3.60 +/- 1.73 ng/ml (mean +/- SD) at Day 30 of pregnancy, to 24.53 +/- 8.81 ng/ml at Day 120, and to 1551.91 +/- 589.68 ng/ml at Day 270. Peak concentration of bPAG was 2462.42 +/- 1017.88 ng/ml and it occurred 1-5 days prior to parturition. After delivery, bPAG concentrations decreased steadily to 499.63 +/- 267.20 ng/ml at Day 14 postpartum (pp), 10.12 +/- 7.84 ng/ml at Day 60 pp, and 1.44 +/- 1.08 ng/ml at Day 90 pp. The undetectable concentration (less than 0.20 ng/ml) was reached by Day 100 +/- 20 pp. An investigation undertaken in Holstein heifers, Holstein cows, and Hereford cows used as recipients for purebred Holstein embryos supplied evidence of the influence of breed of recipient and sex of fetuses on peripheral concentrations of bPAG. A herd of 430 Holstein-Friesian heifers that had received transferred embryos were bled at Day 35 postestrus (pe) for measurement of bPAG. The bPAG was detected in 287 of 430 serum samples analyzed. By rectal palpation performed at Day 45 pe, 267 heifers with detectable levels of bPAG at Day 35 pe were confirmed to be pregnant as were 3 of 143 heifers previously diagnosed as not pregnant by RIA. These results suggest that detection of this placental-specific antigen in the serum could be used as a specific serological method for early pregnancy diagnosis in cattle from 28 days after breeding.

Biodiversity of multiple Pregnancy-Associated Glycoprotein (PAG) family: gene cloning and chorionic protein purification in domestic and wild eutherians (Placentalia) – a review

“…The secretion of PAGs can also differ based on the sex and breed of the foetus. Higher PAG concentration was determined in cows with male foetuses of the same breed, however in Hereford cows with transferred Holstein embryos the PAG concentration was higher in mothers with female foetuses [97].…”

“…The presence of PAGs can be measured by radioimmunologic (RIA) and immunoenzymatic (ELISA) tests. These PAG tests allow for early pregnancy diagnoses in domestic cattle [69,80,91,[95][96][97][98], sheep [70,[99][100][101][102][103][104] and goats [105,106]. Moreover, heterologous PAG tests were also useful for pregnancy diagnoses in wild ruminants, i.e.…”

“…In cattle and goats, the PAG concentration increases as pregnancy progresses [80,97,119]. In sheep, the concentration pattern of the PAGs is biphasic [99,102,104], increases (300−400 ng.mL −1 ) during the second month of pregnancy, when chorionic cells have intensively proliferated and the placenta was formed.…”

Viability of cloned bovine embryos after one or two cycles of nuclear transfer and in vitro culture

“…Two embryos of comparable quality from the same blastomere donor were transferred together into the recipient's uterine horn ipsilateral to the corpus luteum. Pregnancies were diagnosed on Day 35 by pregnancy-associated glycoprotein (PAG) determination (11). All pregnant recipients were examined after 90 d of gestation by palpation per rectum in order to control the ongoing pregnancy.…”

Autoimmunization of ewes against pregnancy-associated glycoproteins does not interfere with the establishment and maintenance of pregnancy

“…Many BNC products are able to gain access to maternal -E-mail: greenjo@missouri.edu tissues (Duello et al, 1986;Liang et al, 1999). Indeed, the modern/BNC-specific PAGs can be found circulating in maternal blood soon after apposition and attachment of the conceptus to the uterine epithelium (Sasser et al, 1986;Zoli et al, 1992;Green et al, 2005). This feature of the modern/ BNC PAGs has been exploited as the basis for pregnancy diagnosis in cattle and related ruminants.…”