title: Hemoglobin vesicles containing methemoglobin and L-tyrosine to suppress methemoglobin formation in vitro and in vivo.
abstract: Hemoglobin (Hb) vesicles have been developed as cellular-type Hb-based O(2) carriers in which a purified and concentrated Hb solution is encapsulated with a phospholipid bilayer membrane. Ferrous Hb molecules within an Hb vesicle were converted to ferric metHb by reacting with reactive oxygen species such as hydrogen peroxide (H(2)O(2)) generated in the living body or during the autoxidation of oxyHb in the Hb vesicle, and this leads to the loss of O(2) binding ability. The prevention of metHb formation by H(2)O(2) in the Hb vesicle is required to prolong the in vivo O(2) carrying ability. We found that a mixed solution of metHb and L-tyrosine (L-Tyr) showed an effective H(2)O(2) elimination ability by utilizing the reverse peroxidase activity of metHb with L-Tyr as an electron donor. The time taken for the conversion of half of oxyHb to metHb (T(50)) was 420 min for the Hb vesicles containing 4 g/dL (620 microM) metHb and 8.5 mM L-Tyr ((metHb/L-Tyr) Hb vesicles), whereas the time of conversion for the conventional Hb vesicles was 25 min by stepwise injection of H(2)O(2) (310 microM) in 10 min intervals. Furthermore, in the (metHb/L-Tyr) Hb vesicles, the metHb percentage did not reach 50% even after 48 h under a pO(2) of 40 Torr at 37 degrees C, whereas T(50) of the conventional Hb vesicles was 13 h under the same conditions. Moreover, the T(50) values of the conventional Hb vesicles and the (metHb/L-Tyr) Hb vesicles were 14 and 44 h, respectively, after injection into rats (20 mL/kg), confirming the remarkable inhibitory effect of metHb formation in vivo in the (metHb/L-Tyr) Hb vesicles.
authors.affiliation: Department of Applied Chemistry, Graduate School of Science and Engineering, Waseda University, Tokyo, 169-8555, Japan.
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Atoji
authors.forename: Motonari
authors.initials: M
authors.lastname: Aihara
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sakai
authors.forename: Eishun
authors.initials: E
authors.lastname: Tsuchida
authors.forename: Shinji
authors.initials: S
authors.lastname: Takeoka
mesh_terms: D000818:Animals; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D008706:Methemoglobin / Q000737:chemistry* / Q000378:metabolism; D016877:Oxidants / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D022161:Transport Vesicles / Q000737:chemistry* / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D006454:Hemoglobins; D016877:Oxidants; D014443:Tyrosine; D008706:Methemoglobin; D006861:Hydrogen Peroxide