Rat alpha-macrofetoprotein (acute-phase alpha 2-macroglobulin) during hepatocarcinogenesis.

Rat alpha-macrofetoprotein (AMF) and alpha-fetoprotein (AFP) are secreted by the fetal liver and become elevated in serum during hepatocarcinogenesis and in animals bearing hepatocellular carcinomas. It has been suggested that these fetal plasma proteins may be influenced by related control mechanisms. The experiments presented herein examined the early responses of these plasma proteins during hepatocarcinogenesis using the hepatocarcinogens acetylaminofluorene and diethylnitrosamine. Under these conditions, AFP serum concentrations were elevated within a few days of exposure to acetylaminofluorene, whereas AMF serum concentrations remained essentially normal. AFP became elevated after a number of weeks of exposure to diethylnitrosamine. In either regimen, AMF became elevated only later when large primary hepatocellular carcinomas were found. The time of appearance of AMF after transfer of an AFP-secreting Morris hepatoma indicated that AMF was elevated only in animals with extremely large, necrotic tumors. Thus, it appears that elevation of serum AFP resulted from either exposure to hepatocarcinogens or production by hepatocellular carcinomas, but that the elevations of serum AMF levels resulted from inflammatory injury or necrosis of tumor tissues.