Abstract
Summary
A plasma protein, designated alpha2 (acute phase) globulin, present in fetal, neonatal, pregnant, and injured adult rats, but not detected in normal adult rats all gave reactions of immunologic identity. Incubation of fetal and neonatal rat liver slices resulted in incorporation of 14C-labeled amino acids into this alpha2 (acute phase) globulin. Under identical experimental conditions, incubation of liver slices from pregnant and normal adult rats did not produce detectable labeling of this plasma protein. These findings suggest that (1) fetal and neonatal liver is the source of the plasma alpha2 (acute phase) globulin detected in such animals: (2) the presence of alpha2 (acute phase) globulin in injured adult rats reflects hepatic synthesis of a normal fetal-specific globulin rather than an “abnormal” injury-specific protein; (3) the DNA cistronic region coding for this globulin is “switched-on” in fetal and neonatal rat liver, is “switched-off” or repressed in normal adult liver, and is again “switched-on” or derepressed in liver of injured adult rats.
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