Alpha-Fetoprotein and albumin synthesis during the cell cycle

The synthesis of alpha-fetoprotein and albumin in two clones of AH66 hepatoma was studied. (1) Amounts of AFP and albumin synthesized by the C-4 clone were 2.9 and 0.28 X 10(-7) mug per cell per hour, respectively. AFP and albumin amounts synthesized by the A-1 clone were 2.5 and 1.8 X 10(-7) mug per cell per hour, respectively. (2) The cell cycles of the C-4 and A-1 clones were as follows: C-4 clone: mean generation time 20.5 hours: G1, 10 hours; S, 7 hours; G2, 4 hours; and M, 30 minutes. A-1 clone: mean generation time 50.7 hours: G1, 36 hours; S, 10 hours; G2, 4 hours; and M, 30-60 minutes. (3) AFP was found to be synthesized from late G1 phase to the end of the S phase for 9 hours in C-4 and 25 hours in A-1. The albumin production was from late S phase to the beginning of the G2 phase for 4 hours in C-4 and 9 hours in A-1, which were approximately half or one-third of the time spent on AFP production. (4) The double staining with fluorescent-conjugated antibodies to AFP and albumin demonstrated that AFP and albumin are probably synthesized by different cells.