AJP - Endocrinology and Metabolism, Vol 245, Issue 2 138-E142, Copyright © 1983 by American Physiological Society
Distribution of acute-phase alpha 2-macroglobulin in rat fetomaternal compartments
D. E. Panrucker, P. C. Lai and F. L. Lorscheider
Rat acute-phase alpha 2-macroglobulin (AP alpha 2M) concentration was
measured by radioimmunoassay in maternal serum, fetal plasma, maternal
liver, fetal liver, and amniotic fluid as a function of gestational and
neonatal age. The concentration profiles of AP alpha 2M in maternal serum
and fetal plasma displayed two peaks, one in early gestation and another
during late gestation. Synthesis of AP alpha 2M was confirmed by the
immunoprecipitation of [35S]methionine incorporated into cultures of
selected tissues. The following observations were made. 1) Maternal serum
concentrations of AP alpha 2M were higher than those observed in fetal
plasma in early gestation. This was attributable to a high level of
maternal AP alpha 2M synthesis in metrial gland which was absent in liver
and moderate in yolk sac. 2) In late gestation fetal plasma concentrations
of AP alpha 2M greatly exceeded those observed in maternal serum. This
could be explained by the pronounced synthesis of AP alpha 2M in fetal
liver that was not apparent in maternal liver or yolk sac. 3) During labor,
a transient increase in AP alpha 2M concentration was observed in maternal
serum and fetal plasma. 4) During lactation a moderately elevated maternal
serum concentration of AP alpha 2M was maintained. 5) Amniotic fluid
concentration of AP alpha 2M was very low throughout gestation, which
indicated that the fetal glomerulus was relatively impermeable to this
large protein. It is concluded that in early gestation a principal maternal
source of AP alpha 2M appears to be the metrial gland, whereas in late
gestation fetal liver is a major source of AP alpha 2M appearing in fetal
plasma from where some of this macroglobulin is speculated to be
transported to the maternal circulation.
