Abstract
NADH-cytochrome c reductase activity of the cell membrane was not significantly inhibited by KCN, NaN3, Antimycin A or rotenone but was evidently inhibited by PCMB and also by NEM. Km values for NADH in NADH-cytochrome c reductase or NADH-ferricyanide dehydrogenase of the cell membrane were almost equal to those in the microsomes. These Km values were hardly affected by administration of CCl44. Cytochrome b5 and P-450 were identified in the cell membrane fraction, and the contents were normally remarkably low as compared with those in the microsomal fraction. However, they increased approx. two-fold following CCl4 administration, while those in microsomes conversely diminished by half. NADH-cytochrorne b5 reductase activity in the cell membrane fraction was approx. onethird as low as NADH-cytochrome c reductase activity. The former was virtually unaffected by administration of CCl4. It is proposed that NADH-cytochrome c reductase in the cell membrane originates from microsomes but not from mitochondria and that increase in the enzyme activity after CCl4 administration may be caused by migration of hemo- and flavo- protein from endoplasmic reticulum to plasma membranes of liver cells in vivo.
