Changes in plasma alpha 1-acid glycoprotein and albumin concentrations during late pregnancy in rhesus monkeys

Plasma protein concentrations are an important determinant of maternal-fetal drug transfer in the perinatal period. Plasma concentrations of alpha 1-acid glycoprotein (AAGP) and albumin were measured in pregnant rhesus monkeys using radial immunodiffusion assays at weekly intervals during the third trimester (n = 12), at 3-day intervals in the 2 weeks prior to full term (n = 10), and at 0, 1, 12, and 60 h after birth (n = 4). AAGP concentrations increased significantly, and albumin concentrations decreased significantly, from weeks 13 to 21 gestation as well as from day 150 gestation to birth. No changes were seen in the postpartum period. AAGP and albumin concentrations were highly negatively correlated from day 150 gestation to birth. The data suggest that AAGP and albumin concentrations are jointly but inversely regulated by physiological or hormonal conditions that precede delivery.