Effect of extra-hepatic Walker sarcoma 256 on the synthesis and degradation of liver cytochromes P-450 and b5.

Abstract

Extra-hepatic Walker sarcoma 256 produced a marked decrease (approximately 60%) in the levels of cytochrome P-450 and NADP-cytochrome P-450 reductase in rat liver endoplasmic reticulum, and a lesser decrease (approximately 20%) of cytochrome b5 and NADH-cytochrome b5 reductase. Polychlorinated biphenyls induced the synthesis of these cytochromes and reductases to approximately the same extent both in normal and tumor-bearing rats. The double-label technique was used to demonstrate that the synthesis of cytochromes P-450 and b5 was reduced in the liver of tumor-bearing rats. The turnover of P-450 was not affected by the tumor, whereas cytochrome b5 turnover was decreased. It is proposed that Walker sarcoma 256 mainly affects the transcription of cytochromes P-450 and b5 through a toxohormone, and that a regulatory mechanism coordinates the level of each cytochrome and its respective reductase.

• Authors: I Raw
• Journal: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas (Braz J Med Biol Res) Vol. 16 Issue 4 Pg. 291-5 (Dec 1983) ISSN: 0100-879X [Print] Brazil
• PMID: 6424747 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Cytochrome b Group
• Cytochrome P-450 Enzyme System
• Polychlorinated Biphenyls
• Cytochrome Reductases

Topics

• Animals
• Carcinoma 256, Walker (enzymology)
• Cytochrome P-450 Enzyme System (metabolism)
• Cytochrome Reductases (metabolism)
• Cytochrome b Group (metabolism)
• Female
• Microsomes, Liver (enzymology)
• Polychlorinated Biphenyls (pharmacology)
• Rats