Preferential S-sulfonate formation in lung and aorta.

Area of Science:

• Biochemistry
• Physiology
• Toxicology

Background:

• S-sulfonate (S-SO-3) compounds are known plasma metabolites of sulfite in mammals.
• Understanding sulfite metabolism in vital organs is crucial for assessing its physiological impact.

Purpose of the Study:

• To investigate the formation and characteristics of S-sulfonates in rabbit aorta and lung lobes following intravenous sulfite exposure.
• To determine the kinetics and clearance rates of S-sulfonate formation in these tissues.

Main Methods:

• Rabbits were infused intravenously to maintain constant arterial sulfite concentrations (approx. 550 microM).
• S-sulfonate concentrations in aorta and lung tissues were quantified.
• In vitro experiments were conducted to study reaction kinetics in aorta tissue.
• Clearance of S-sulfonates from tissues was monitored over time.

Main Results:

• Non-diffusible and stable S-sulfonates were formed in rabbit aorta and lung lobes.
• S-SO-3 formation followed first-order kinetics with coefficients of 0.3–0.4 h-1.
• Asymptotic concentrations reached approximately 900 nmol/g dry wt. in lung and 9000 nmol/g dry wt. in aorta.
• In vitro kinetics in aorta closely matched in vivo observations.
• S-SO-3 clearance from both tissues was first-order with a half-life of 2–3 days.

Conclusions:

• Sulfite exposure leads to the formation of stable S-sulfonate metabolites in the aorta and lungs.
• The observed kinetics and slow clearance suggest potential for tissue accumulation.
• These findings highlight the importance of considering S-sulfonate formation in sulfite toxicity and metabolism studies.