title: Effects of endogenous ascorbate on oxidation, oxygenation, and toxicokinetics of cell-free modified hemoglobin after exchange transfusion in rat and guinea pig.
abstract: Chemically modified hemoglobin (Hb) solutions are promising oxygen therapeutics; however, these agents are prone to intravascular oxidation. Using a 50% exchange transfusion (ET) model with bovine polymerized hemoglobin (PolyHbBv), we examined heme oxidation, oxygenation markers, and toxicokinetics in rats, an ascorbic acid (AA)-producing species, and in guinea pigs, a non-AA-producing species. Plasma AA decreased by 50% in guinea pigs after ET, but it was unchanged in rats for the first 20 h post-ET. Both species cleared PolyHbBv from the circulation at similar rates. However, exposure to ferric PolyHbBv over time was 5-fold greater in the guinea pig. Mass spectrometry analysis of plasma revealed oxidative modifications within the tetrameric fraction of PolyHbBv in guinea pig. Oxygen equilibrium curves of PolyHbBv measured in plasma after ET were more left-shifted in guinea pigs compared with rats, consistent with increased ferric PolyHbBv formation. Renal hypoxia-inducible factor (HIF)-1alpha, whose activity strictly depends on the partial pressure of oxygen increased over time, and it correlated inversely with circulating ferrous PolyHbBv in both species. Interestingly, HIF-1alpha activity was greater in guinea pigs compared with rats at 72 h post-ET. Mean arterial pressure increases were also greater in guinea pigs; however, minimal differences in cardiac and renal pathology were observed in either species. The present findings suggest the importance of plasma AA in maintaining the stability of acellular Hb susceptible to oxidation, and they may be relevant to humans, which display a similar plasma/tissue antioxidant status to guinea pig.
authors.affiliation: Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA. paul.buehler@fda.hhs.gov
authors.forename: Paul W
authors.initials: PW
authors.lastname: Buehler
authors.forename: Felice
authors.initials: F
authors.lastname: D'Agnillo
authors.forename: Victoria
authors.initials: V
authors.lastname: Hoffman
authors.forename: Abdu I
authors.initials: AI
authors.lastname: Alayash
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000097:blood*; D001794:Blood Pressure / Q000187:drug effects; D001802:Blood Substitutes / Q000493:pharmacokinetics / Q000494:pharmacology / Q000633:toxicity; D002417:Cattle; D002474:Cell-Free System; D004355:Drug Stability; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D006454:Hemoglobins / Q000493:pharmacokinetics / Q000494:pharmacology / Q000633:toxicity; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000473:pathology; D008297:Male; D009206:Myocardium / Q000473:pathology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000097:blood*; D010951:Plasma Exchange; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001802:Blood Substitutes; D006454:Hemoglobins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C037158:polyhemoglobin; D001205:Ascorbic Acid; D010100:Oxygen