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Correlation of phenylalanine hydroxylase activity with cell density in cultured hepatoma cells

1975; Elsevier BV; Volume: 90; Issue: 1 Linguagem: Inglês

10.1016/0014-4827(75)90353-5

1090-2422

Daniel McClure, Michael R. Miller, Ross Shiman,

Plant Gene Expression Analysis

Abstract We have found that the specific activity of phenylalanine hydroxylase varies over at least a forty-fold range during the growth cycle of Reuber hepatoma (H4) cells growing in monolayer culture. The variation has three phases: (1) a very rapid drop in specific activity upon subculturing to a low cell density; (2) a region of low specific activity and (3) after confluency, a rise to a high specific activity. All the results indicate that the cell density in the culture dish is primarily responsible for this fall and rise in activity. Neither conditioning of the growth medium, the rate of cell division, nor enzyme leakage from the cells appear to play a major role in the changes observed. Lactic dehydrogenase specific activity was determined in all experiments; a much smaller, but still cell density-dependent variation was observed for this enzyme.