DECREASED INTRACELLULAR PROTEOLYSIS CORRELATES WITH THE MAINTENANCE OF A SPECIFIC ISOENZYME OF CYTOCHROME P‐450

The rates of intracellular protein degradation, of identically labelled populations of proteins, were compared in hepatocytes cultured at 37° (on an adsorbed collagen layer) and in cells preserved on gelatin gels at 10°C. The half‐lives of the long‐lived proteins were 35.4±8.6h ( N =4) and 692.9±216.9h ( N =4) respectively. Proteolysis was substantially decreased at 10°C but the rate of decrease remained constant. Hepatocytes rapidly removed resorufin from the culture medium. The resorufin was not being conjugated or accumulated within the cells. Dicumarol, a potent inhibitor of quinone oxidoreductase, at high concentration (500μm) caused only a 72% decrease in the utilization of resorufin. The microsomal detoxifying enzyme, cytochrome P‐450 1A1 remained at a constant level in the preserved hepatocyte monolayers. The results of this study strongly favour storing hepatocytes at 10°C rather than at 4° or 37°C.