Characterization of serum alpha 1-acid glycoprotein in fetal and newborn calves during development.

Serum alpha 1-acid glycoprotein (alpha 1-AG) in bovine fetuses and newborn calves was characterized. Serum alpha 1-AG concentration increased during fetal development and neonatal stages. Mean +/- SD serum alpha 1-AG concentration reached a peak of 1,368 +/- 207 micrograms/ml immediately after birth, but thereafter gradually decreased to 249 +/- 100 micrograms/ml, similar to the normal adult bovine range. By use of isoelectric focusing of thin-layer gels, we detected 7 microheterogeneity bands ranging from pI 3.2 to 3.8 in adult bovine serum. Twelve bands ranging from pI 2.6 to 3.8 were found in 9-month fetuses and in neonates. The 5 most-acidic bands, which are absent in adult serum, ranged between pI 2.6 and 3.1 and decreased with maturation as band patterns assumed adult characteristics. By crossed affinity electrophoresis, alpha 1-AG of adult bovine serum was separated into 4 peaks according to its differential affinity to concanavalin A (conA). Seventy-five percent of the alpha 1-AG concentration was represented by peak 3 (P-3) and peak 4 (P-4), which had moderate or strong binding to conA. In contrast, fetal sera contained only peak 1 (P-1), which did not have conA-binding affinity. In neonatal sera, 4 peaks were recognized, of which P-1 comprised 70% of the total alpha 1-AG. Thereafter, with aging, percentage of P-3 and P-4 increased as band composition approached the normally expected adult pattern.