Synthesis of cytochrome P-450 in isolated liver cells during exposure to hyperoxia.

: Mouse hepatocytes were separated within 15 min of the death of the animal. A method of determining cytochrome P-450 was developed and used to show that cells prepared quickly still contained normal levels of this pigment. Cells suspended in complete culture medium were exposed to various partial pressures of oxygen for 30 min. When exposed to anoxia there was a 30% loss of cytochrome; at 30-50 Torr, a 30% increase; to 150 Torr, a 10% decrease; and to 700 Torr or higher, 30%-60% increase. The time course of the increase, at those tensions at which it was obtained, showed the increase occurred for 1 to 2 h and was followed by a continual loss. This final loss was at approximately the same rate at all tensions, whether or not there was an initial rise. Thus the cytochrome P-450 levels of isolated hepatocytes show qualitatively the same response to varying oxygen tensions that they do in intact animals.