Intact organ spectrophotometry and single-photon counting

Area of Science:

• Toxicology
• Biochemistry
• Cellular Biology

Background:

• Assessing enzyme levels and capacities is crucial in toxicology.
• Developing methods for determining actual concentrations and fluxes in intact cells and organs is essential.
• Noninvasive techniques, particularly photometric methods, have been developed for this purpose.

Purpose of the Study:

• To explore the utility of noninvasive photometric techniques for toxicological assessments.
• To monitor cytochromes, cytochrome P-450, and other pigments in intact organs.
• To investigate the generation of photoemissive species, such as singlet molecular oxygen and excited carbonyls, in toxicological contexts.

Main Methods:

• Transmission spectrophotometry was used to monitor pigments in solid organs.
• Photoemission monitoring was employed to detect singlet molecular oxygen and excited carbonyls.
• Menadione metabolism was studied, including the effects of inhibiting Phase II enzymes and DT diaphorase.

Main Results:

• Transmission spectrophotometry allows monitoring of mitochondrial respiratory chain cytochromes, cytochrome P-450, and other pigments.
• Steady-state levels of catalase Compound I in the liver provide insights into hydrogen peroxide (H2O2) production rates.
• Inhibition of Phase II enzymes or DT diaphorase increased singlet molecular oxygen levels during menadione metabolism.
• Induction of DT diaphorase by BHA pretreatment decreased reactive oxygen species levels.

Conclusions:

• Noninvasive photometric techniques are valuable tools in toxicology for assessing cellular function and reactive species.
• Monitoring photoemission provides insights into the generation of reactive oxygen species during xenobiotic metabolism.
• Understanding enzyme roles, like DT diaphorase, in redox cycling is critical for mitigating toxicological damage.