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Coronary vascular actions of stroma-free hemoglobin preparations
G P Biro1, G C Taichman, B Lada
1Department of Physiology, School of Medicine, University of Ottawa, Ontario, Canada.
Insights
Stroma-free hemoglobin solutions (SFHS) were tested in canine coronary arteries. Unmodified SFHS caused vasoconstriction, while modified SFHS did not, indicating vascular activity in both preparations.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
Background:
- Stroma-free hemoglobin solutions (SFHS) are investigated as potential blood substitutes.
- Understanding the vascular effects of SFHS is crucial for their clinical application.
Purpose of the Study:
- To evaluate the coronary vascular actions of unmodified and pyridoxylated, cross-linked SFHS.
- To compare the effects of SFHS with whole blood in a canine coronary artery model.
Main Methods:
- Anesthetized, open-chest dogs were used with the left anterior descending coronary artery as a test bed.
- Coronary flow was measured during perfusion with whole blood, unmodified SFHS, and modified SFHS.
- Vascular responses to adenosine and reactive hyperemia were assessed.
Main Results:
- Unmodified SFHS induced significant coronary vasoconstriction.
- Pyridoxylated, partially polymerized SFHS did not cause vasoconstriction.
- Both SFHS preparations altered coronary flow-autoregulation and impaired the reactive hyperemia response.
Conclusions:
- Both unmodified and pyridoxylated cross-linked SFHS exhibit vascular activity in the canine coronary circulation.
- Pyridoxal modification appears to mitigate the vasoconstrictive effects of SFHS.
- Further research is needed to fully characterize the vascular actions of SFHS.
Abstract:
The left anterior descending coronary artery was cannulated in anesthetized, open-chest dogs for use as a coronary test bed to assess the coronary vascular actions of oxygenated, unmodified and pyridoxylated, partially cross-linked (polymerized), stroma-free hemoglobin solutions (SFHS). The actions of these SFHSs were assessed in this test bed, by comparison with perfusion with whole blood. Unmodified SFHS caused significant vasoconstriction, whereas pyridoxylated, partially polymerized SFHS did not do so. The existing coronary flow during perfusion with either SFHS preparation, under basal conditions, did not increase during intracoronary infusion of adenosine. Coronary flow-autoregulation was also altered during perfusion with either SFHS, because the "normal" reactive hyperemia response, observed in the control experiments, was not seen. These findings suggest that both unmodified and pyridoxylated cross-linked (70% polymers) hemoglobin preparations possess some vascular activity when tested in the canine coronary circulation.