[Characterization of guinea pigs after adaptation to different high vitamin C supplies. 3. Microsomal cytochromes in the liver and kidney].

The specific amounts of the microsomal cytochromes P-450 (P-454) and b5 and the amounts of microsomal protein in liver and renal cortex of guinea pigs depend on the extent of the vitamin C supply to which the animals are adapted (at least 6 weeks). In the case of low supply--with 5 mg vitamin C in 100 g food--which still permits to survive, the amounts of the cytochromes are decreased in both organs (an accumulative supply--every 3.5 days via stomach tube--causes no evident decreases). The reduced amount of cytochrome P-450 gives rise to a corresponding elongation of the sleeping time after injection of evipane; this agrees with other reports upon restriction of metabolic activities by marginal supply. But the amount of the cytochrome is induced as well in these animals by several injections of evipane, to the same level as in animals supplied with more vitamin C. Our early report on a considerable decrease of the specific amount of cytochrome P-450 in the liver by omission of vitamin C for 14 days proves correct only in this organ and when the guinea pigs were previously abundantly supplied with vitamin C. There is no corresponding decrease after an adaptation to medium and lesser supplies of vitamin C. The decrease of the cytochrome after abundant supply seems to be due to a diminished stimulation of its synthesis in connection with modifications in the hormonal control of the metabolism and, thus, is only indirectly connected with the lack of vitamin C. The effects of omission of vitamin C supply probably depend generally on the previous adaptation, at least in the liver. The considerable decrease of the cytochrome P-450 and the simultaneous reduction of the mitochondrial compartment raise the question of if a maximum supply with vitamin C is favorable resp. the physiological optimum.