Decrease in the activity of hepatic microsomal drug-metabolizing enzymes in tumor-bearing nude mice

Area of Science:

• Pharmacology
• Biochemistry
• Cancer Biology

Background:

• Hepatic microsomal drug-metabolizing enzymes are crucial for xenobiotic and endogenous compound processing.
• Tumor-bearing hosts often exhibit altered drug metabolism, impacting treatment efficacy.
• Nude mice (BALB/c-nu/nu) are valuable models for studying human tumors due to their immunodeficiency.

Purpose of the Study:

• To investigate the impact of tumors on hepatic microsomal drug-metabolizing enzyme activities in nude mice.
• To determine if observed enzyme activity changes are linked to immunoreactivity or cachexia.

Main Methods:

• Assessed cytochrome P-450 content in tumor-bearing nude mice.
• Measured activities of key drug-metabolizing enzymes: cyclophosphamide oxidase, benzo[a]pyrene hydroxylase, aniline hydroxylase, and benzphetamine N-demethylase.
• Compared enzyme levels and activities in tumor-bearing mice with control groups (implied).

Main Results:

• Marked decreases in cytochrome P-450 content were observed.
• Significant reductions in the activities of cyclophosphamide oxidase, benzo[a]pyrene hydroxylase, aniline hydroxylase, and benzphetamine N-demethylase were noted.
• These enzyme alterations occurred in nude mice bearing tumors of both human and nude mouse origin.

Conclusions:

• Tumor burden in nude mice leads to a significant decrease in hepatic microsomal drug-metabolizing enzyme activities.
• The observed reductions are not attributable to the host's immune response or cachexia.
• These findings suggest a direct influence of the tumor on the metabolic capacity of the liver.