title: Hemoglobin encapsulation in vesicles retards NO and CO binding and O2 release when perfused through narrow gas-permeable tubes.
abstract: Intravenous administration of cell-free Hb induces vasoconstriction and circulatory disorders, presumably because of the intrinsic affinities to endogenous nitric oxide (NO) and carbon monoxide (CO) as vasorelaxation factors and because of the facilitated O(2) release that might induce autoregulatory vasoconstriction. We examined these gas reactions when Hb-containing solutions of four kinds were perfused through artificial narrow tubes at a practical Hb concentration (10 g/dl). Purified Hb solution, polymerized bovine Hb (Poly(B)Hb), encapsulated Hb [Hb-vesicles (HbV), 279 nm], and red blood cells (RBCs) were perfused through a gas-permeable narrow tube (25 microm inner diameter) at 1 mm/s centerline velocity. The level of reactions was determined microscopically based on the visible-light absorption spectrum of Hb. When the tube was immersed in NO and CO atmospheres, both NO binding and CO binding of deoxygenated Hb (deoxy-Hb) and Poly(B)Hb in the tube was faster than those of HbV and RBCs, and HbV and RBCs showed almost identical binding rates. When the tube was immersed in a N(2) atmosphere, oxygenated Hb and Poly(B)Hb showed much faster O(2) release than did HbV and RBCs. Poly(B)Hb showed a faster reaction than Hb because of the lower O(2) affinity of Poly(B)Hb than Hb. The diffusion process of the particles was simulated using Navier-Stokes and Maxwell-Stefan equations. Results clarified that small Hb (6 nm) diffuses laterally and mixes rapidly. However, the large-dimension HbV shows no such rapid diffusion. The purely physicochemical differences in diffusivity of the particles and the resulting reactivity with gas molecules are one factor inducing biological vasoconstriction of Hb-based oxygen carriers.
authors.affiliation: Research Institute for Science and Engineering, Waseda University, Tokyo, Japan. hiromi@waseda.jp
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sakai
authors.forename: Naoto
authors.initials: N
authors.lastname: Okuda
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sato
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yamaue
authors.forename: Shinji
authors.initials: S
authors.lastname: Takeoka
authors.forename: Eishun
authors.initials: E
authors.lastname: Tsuchida
mesh_terms: D001802:Blood Substitutes / Q000378:metabolism; D002248:Carbon Monoxide / Q000378:metabolism*; D004058:Diffusion; D004912:Erythrocytes / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008081:Liposomes / Q000378:metabolism*; D008833:Microcirculation; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010316:Particle Size; D014661:Vasoconstriction
chemical_list: D001802:Blood Substitutes; D006454:Hemoglobins; D008081:Liposomes; D009569:Nitric Oxide; D002248:Carbon Monoxide; D010100:Oxygen