Microsomal heme oxygenase, the rate-limiting enzyme in the oxidative breakdown of hemin
to bile pigment, has recently been described and characterized. In untreated rats, this
enzyme was found to be most active in spleen, followed by bone marrow, liver, brain, kidney,
and lung. Splenectomy increased heme oxygenase activity of liver microsomes two-to
threefold; injection of hemoglobin or methemalbumin, two-to sevenfold; and experimental
hemolytic anemia, three-to fivefold. By contrast, anemia following blood loss failed to …