Asialoglycoprotein receptor expression in murine pregnancy and development.

Hepatic asialoglycoprotein receptor activity of pregnant mice increased from the tenth day of gestation, reaching 3-fold the normal adult level just prior to parturition and returning to normal within 1 week postpartum. Increases in activity involved both intracellular and cell-surface associated receptors and were associated with enhanced endocytosis of asialoorosomucoid by isolated hepatocytes. Modulation of hepatic binding protein expression during murine pregnancy represents the first situation in which this receptor's concentration has been shown to exceed normal levels in response to a physiologic change. In the fetus, receptor activity was barely detectable throughout gestation, steadily increased in the neonatal period, and reached adult levels by the fifth postpartum day.