Cobalt induction of hepatic heme oxygenase; with evidence that cytochrome P-450 is not essential for this enzyme activity. Academic Article uri icon

Overview

abstract

  • Treatment of rats in vivo with cobalt chloride stimulated heme oxidation by hepatic microsomes to levels up to 800% above controls. This treatment also caused increases in liver weight and in total microsomal protein; in contrast, marked decreases were produced in microsomal oxidation of ethylmorphine (80%), and in cytochrome P-450 (60-70%) and heme (30-50%) contents. Cobalt chloride treatment did not affect heme oxidation by the spleen heme oxygenase system. The rate of heme oxidation by hepatic microsomal enzymes and the microsomal content of cytochrome P-450 were found to be unrelated. This conclusion was reached from studies in which microsomal heme oxygenase activity from cobalt-treated animals could be increased by 900% above control levels in the same microsomal preparation in which cytochrome P-450 content was decreased to spectrally unmeasurable amounts after incubation with 4 M urea. The same treatment eliminated ehtylmorphine demethylation and decreased microsomal NADPH-cytochrome c reductase (EC 1.6.2.4) activity by 75%. It is concluded that (i) the hepatic microsomal enzyme system that oxidizes heme compounds is not the same as that which metabolizes drugs, (ii) cytochrome P-450 is not essential for the oxidation of heme by liver cells, (iii) there is no direct relationship between the rate of heme oxidation and the level of NADPH-cytochrome c reductase activity, and (iv) the oxidation of heme is protein-dependent and the active proteins are inducible, but are different from those involved in drug metabolism.

publication date

  • November 1, 1974

Research

keywords

  • Cobalt
  • Cytochrome P-450 Enzyme System
  • Microsomes, Liver
  • Mixed Function Oxygenases

Identity

PubMed Central ID

  • PMC433868

Scopus Document Identifier

  • 0006476631

PubMed ID

  • 4530983

Additional Document Info

volume

  • 71

issue

  • 11