Coronary vascular actions of stroma-free hemoglobin preparations.

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.