Enhanced oxygen unloading by an interdimerically crosslinked hemoglobin in an isolated perfused rabbit heart

Area of Science:

• Biochemistry
• Cardiovascular Physiology
• Biomaterials

Background:

• Normal hemoglobin (Hb) has limitations in oxygen delivery, particularly under varying physiological conditions.
• Intramolecularly crosslinked hemoglobin (HbXL) was developed to enhance oxygen unloading properties.
• Understanding HbXL's efficacy in cardiac perfusion is crucial for clinical applications.

Purpose of the Study:

• To evaluate the advantages of HbXL over ordinary Hb in coronary perfusion.
• To assess HbXL's oxygen unloading capacity and its impact on cardiac mechanical performance.
• To determine HbXL's utility in low-temperature conditions relevant to cardiac surgery and organ preservation.

Main Methods:

• Coronary perfusion studies were conducted using HbXL and normal Hb.
• Oxygenation curves and tissue oxygen pressures were analyzed.
• Cardiac mechanical performance (contractility, dp/dt) was measured after 90 minutes of perfusion.
• Experiments were performed at varying heart rates, perfusion rates, and oxygen concentrations, including low temperatures (10°C).

Main Results:

• HbXL demonstrated significantly greater oxygen unloading to the heart compared to normal Hb across various conditions.
• Improved oxygen unloading with HbXL occurred at higher tissue oxygen pressures.
• HbXL-perfused hearts maintained superior mechanical performance (two-thirds original contractility) versus Hb-perfused hearts (one-fifth).
• HbXL effectively unloaded oxygen at low temperatures (10°C), unlike whole blood.

Conclusions:

• HbXL offers significant advantages over ordinary Hb in coronary perfusion due to enhanced oxygen unloading.
• The improved oxygen delivery by HbXL supports better cardiac mechanical function.
• HbXL's efficacy at low temperatures makes it a promising agent for supporting aerobic metabolism during cardiac surgery and organ preservation.