Hormonal regulation during secretion of alpha-fetoprotein in hepatoma cells grown in synthetic medium

• Published in: The Journal of biological chemistry Vol. 260; no. 30; pp. 16316 - 16320
• Main Authors: Tsukada, Y, Hibi, N, Ohkawa, K
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 25.12.1985; American Society for Biochemistry and Molecular Biology
• Subjects: alpha-Fetoproteins - metabolism; Animals; Biological and medical sciences; Cell Division - drug effects; Cell Line; Cell physiology; Dexamethasone - pharmacology; DNA Replication - drug effects; DNA, Neoplasm - analysis; Fundamental and applied biological sciences. Psychology; Insulin - pharmacology; Kinetics; Liver Neoplasms, Experimental - metabolism; Methionine - metabolism; Molecular and cellular biology; Rats; Secretion. Exocytosis; Cell culture; Protein hormone; Intracellular transport; Regulation(control); Dexamethasone; Reuber hepatoma; Steroid hormone; Secretion; Biosynthesis; α-Fetoprotein; Insulin; Tumor cell
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)36238-5

The variant cell line of H4-II-E-C3 cells derived from the Reuber H-35 hepatoma cells has been established using protein- and lipid-free synthetic medium. This H4-II-E-C3-V line can synthesize and secrete considerable amounts of alpha-fetoprotein (AFP) and albumin. The addition of 5 X 10(-7) M dexamethasone to the medium stimulated the excretion of AFP without increasing total AFP synthesis, whereas 8.7 X 10(-8) M insulin inhibited the excretion of AFP without a significant inhibition of intracellular AFP synthesis. However, neither dexamethasone nor insulin altered either the cellular or secreted levels of albumin. Cells were pulse labeled with [35S]methionine and then chased after addition of excess unlabeled methionine. AFP appeared in the medium after 10 min, and 50% of the protein was secreted after 110 min. The rate of secretion of AFP was much slower than that of albumin, 50% of which was secreted after 25 min. Dexamethasone, 5 X 10(-7) M, caused a marked enhancement in the rate of AFP secretion, with 50% released after 75 min. Insulin, 8.7 X 10(-8) M, by contrast, caused a marked delay in AFP secretion with only 20% released after 180 min and then a plateau was approached. Since the intracellular AFP was excreted 55% after 180 min the remaining 25% of newly made AFP was suggested to be degraded during secretion. The kinetics of movement of AFP during secretion and endoglycosidase H treatment of intracellular and secreted AFP suggested that insulin impeded the transport of AFP from the rough endoplasmic reticulum to the Golgi apparatus.