Serum concentrations of alpha-macrofeto-protein (acute-phase alpha2-macroglobulin), a proteinase inhibitor, in pregnant and neonatal rats and in rats with acute inflammation.

Alpha macrofetoprotein (AMF) or acute-phase alpha2 macroglobulin serum concentrations are elevated in pregnant, fetal, and newborn rats and in rats with experimentally induced acute inflammation when quantitated using a double-antibody radioimmunoassay. Concentrations of AMF are 17 +/- 2 microgram/ml and 32 +/- 6 microgram/ml in normal adult rat sera. Both maternal (1.2 mg/ml) and neonatal (9.3 mg/ml) concentrations are maximal at term. AMF serum concentrations of rats injected with croton oil into the hind footpads are unchanged for the first 4 h after injection, then increase to a maximum of 10.5 mg/ml 36 h after injection. Serum AMF concentrations correlate directly with the dose of croton oil and the increase in size (swelling) of the injured foot, and remain elevated during the course of inflammation for at least two weeks. The possible function of AMF as an antiproteinase limiting the extent of inflammation after acute tissue injury is discussed.