Detection of a vasoconstrictor factor in stroma-free haemoglobin solutions

Polymerised pyridoxylated haemoglobin solution (PPSFH) is a modified haemoglobin solution which has a normal oxygen carrying capacity, long half-life, and reasonable oxygen affinity, and is a leading candidate for use as an oxygen carrying blood substitute. Previous work has given indications that vasoactive factors may be present. A bioassay sensitive to vasoconstrictors was constructed. PPSFH prepared by chloroform extraction produced a mean pressure rise of 24.3 mm Hg. PPSFH prepared by a crystallisation method showed a mean rise of 2 mm Hg (p = 0.0004). Unmodified stroma-free haemoglobin (SFH) prepared from platelet- and white cell-free red blood cells showed a mean rise of 32.5 mm Hg. These data indicate that both PPSFH and SFH contain a vasoconstrictor factor which is of low molecular weight, is hydrophilic, and is derived from red blood cells.