Oxygen binding of modified hemoglobins in solution.
SFHS modified by covalent incorporation of pyridoxal phosphate using NaCNBH3 as reducing agent had P50 values of 21-25mm Hg, and was insensitive to the addition of BPG. The Hill slope of the modified product was 2.34, demonstrating good functional cooperativity of the subunits. Oxygen carrying capacity, calculated as the ratio of O2 content to the concentration of functional hemoglobin, was found to be about 1.3, very close to the "textbook" ratio of 1.34 for whole blood. These values were achieved with oxygen saturation values over 90% and methemoglobin levels of less than 3%. The results obtained from pyridoxalation using NaCNBH3 contrasted sharply with those obtained using NaBH4, which yielded a product having high oxygen affinity and high methemoglobin values. This latter product was poorly saturated with oxygen at ambient pressures and demonstrated a significantly lowered oxygen carrying capacity. The NaBH4 product was also insensitive to the addition of BPG; the reason for this was not ascertained. SFHS-P by the borohydride method thus exhibited marked deficiencies relative to that prepared with cyanoborohydride, as defined by the characterizations employed for this study.
Mauldin
D
D
Department of Physiology, University of Ottawa, Canada.
Dalpé
R L
RL
Anderson
P J
PJ
Biro
G P
GP
D001894:Borohydrides / Q000494:pharmacology; D006454:Hemoglobins / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008706:Methemoglobin / Q000378:metabolism; D010108:Oxyhemoglobins / Q000378:metabolism*; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D012996:Solutions
D001894:Borohydrides; D006454:Hemoglobins; D010108:Oxyhemoglobins; D012996:Solutions; D011732:Pyridoxal Phosphate; D008706:Methemoglobin; C009282:sodium cyanoborohydride