Isolation and partial characterization of a rifampicin induced rabbit liver microsomal cytochrome P-450

Area of Science:

• Biochemistry
• Pharmacology
• Enzymology

Background:

• Cytochrome P-450 enzymes play crucial roles in drug metabolism and steroid hydroxylation.
• Rifampicin is known to induce certain cytochrome P-450 isoforms.
• Understanding specific P-450 forms like LM3 is important for drug-drug interactions and metabolic studies.

Purpose of the Study:

• To investigate the effect of rifampicin administration on cytochrome P-450 expression in rabbits.
• To purify and characterize the rifampicin-induced LM3 form of cytochrome P-450.
• To determine the relationship between the rifampicin-induced LM3 form and other P-450 isoforms.

Main Methods:

• Administration of rifampicin to male New Zealand rabbits.
• Purification of the induced cytochrome P-450 enzyme to electrophoretic homogeneity.
• Spectroscopic analysis (UV-Vis) of the purified enzyme.
• Immunological assays and enzymatic activity measurements, including stereospecific progesterone hydroxylation.

Main Results:

• Rifampicin increased the concentration of LM3 cytochrome P-450 to 30% of total microsomal P-450.
• The enzyme was purified with an 8% yield.
• The purified enzyme exhibited a characteristic absorption maximum at 449 nm in its reduced CO-complexed form.
• Enzyme activity and immunological assays indicated a relationship between LM3 (induced by rifampicin) and LM3c (from untreated rabbits).

Conclusions:

• Rifampicin induces a specific cytochrome P-450 isoform (LM3) in rabbits.
• The purified LM3 enzyme possesses distinct biochemical and spectral properties.
• LM3 shares immunological and functional similarities with LM3c, suggesting potential functional overlap or precursor-product relationships.