H2S during circulatory shock: some unresolved questions.

Area of Science:

• Physiology
• Biochemistry
• Pharmacology

Background:

• Hydrogen sulfide (H2S) plays a critical role in circulatory shock.
• Understanding vascular sulfide concentrations is vital, especially in "acute on chronic disease" contexts.
• Existing literature presents a wide range of reported sulfide blood levels during circulatory shock.

Purpose of the Study:

• To determine accurate "real" sulfide levels during circulatory shock.
• To investigate how injury and co-morbidity affect H2S-producing enzyme expression in shock.

Main Methods:

• Literature review of studies on H2S levels and H2S-producing enzyme expression in circulatory shock.
• Analysis of variability in reported sulfide levels due to analytical methods, models, and species.
• Evaluation of data on tissue expression of cystathionine-gamma-lyase (CSE) and cystathionine-beta-synthase (CBS) during shock.

Main Results:

• Reported sulfide levels during shock vary significantly, influenced by methodology and experimental design.
• Some reported high H2S levels warrant scrutiny due to known H2S toxicity.
• Constitutive CSE expression appears crucial for kidney function; increased CBS and CSE in lung/liver suggest adaptive responses to stress.

Conclusions:

• Accurate "on line" H2S measurement techniques are lacking, making premature to correlate levels with shock severity or therapeutic outcomes.
• Constitutive CSE expression is important for organ function, particularly renal.
• Upregulation of CBS and CSE in stress states like circulatory shock indicates an adaptive response.