Abstract
Cytochrome b5 was isolated from liver microsomes using a detergent-method. The hemoprotein was found to bind to liver plasma membranes in vitro and was accompanied by an increase in NADH-cytochrome c reductase activity, but not NADH-ferricyanide reductase activity. As in the case of microsomes, the binding to plasma membranes was temperature-dependent and was tight to the extent that the bound cytochrome b5 was little released under high ionic strength. The capacity of plasma membranes for the binding was less than that of microsomes. Administration of CCl4 did not significantly affect the binding of the hemoprotein in both fractions. These results add support to our previous proposal that the elevation of NADH-cytochrome c reductase activity of liver plasma membranes observed early after administration of CCl4 may be caused by the binding of cytochrome b5 which has probably migrated from the endoplasmic reticulum.
