Intracellular synthesis of alpha-fetoprotein and fibrinogen without secretion by Zajdela rat ascites hepatoma cells.

Transplabtable Zajdela rat ascites hepatoma cells, previously considered "nonproducers," synthesize detectable amounts of intracellular alpha-fetoprotein (AFP) and fibrinogen, but fail to secret or release these serum proteins. Evidence for defective secretory mechanisms for serum proteins in these hepatoma cells (a) explains the failure to detect AFP in either the serum or ascitic fluid of rats bearing this hepatoma, (b) indicates that some hepatoma cells should be classified as "nonsecretors," rather than nonproducers of AFP, and (c) suggests that failure to detect AFP in some human and animal hepatomas in vivo and in vitro may also reflect failure of secretion rather than failure of intracellular synthesis.