Meeting Abstract
54.5 Tuesday, Jan. 6 Hemoglobin Polymerization in Fishes: A Physiological Antioxidant? HUNT VON HERBING, I*; CASHON, ; BABCOCK, ; University of North Texas; University of Maine; Dahl-Chase Diagnostics vonherbing@unt.edu
Observations of teleost red blood cells have shown that regular paracrystalline arrays of polymerized hemoglobin (Hb) tetramers form under low oxygen and low pH conditions in several species, including Atlantic cod (Gadus morhua) and Atlantic Toadfish (Opsanus tau). The phenomenon of Hb polymerization is also termed hemoglobin gelation and/or sickling, and its physiological characteristics, importance to physiology, and survival is presently unknown. In this study, data were obtained on the frequency and physiological nature of Hb gelation in fishes that inhabit several different environments from the Arctic, boreal and tropical regions. Thirty-three fish species were examined for the occurrence of gelation and only 13 exhibited the trait. Further, in these 13 species, 100% of the red blood cells became crystallized when exposed to hypoxia and/or low pH. Evidence for the formation and presence of the paracrystalline Hb matrix in whole red blood cells was provided by light microscopy, transmission electron microscopy and was supported by in situ observations. Data provided by purification and subsequent polymerization of the Hb extracted from whole blood showed that gelation is an intrinsic property of the Hb, not dependent on the surrounding intracellular matrix, likely occurs in conditions that are found in vivo, and may occur in fishes found in several environments. Proposed models of Atlantic cod Hb constructed by homology modeling of the primary Hb sequence found that at least three amino acid substitutions have occurred in the Hb beta chains. Two of these substitutions result in extra cysteines that may induce polymerization by forming interchain disulphide bonds. These disulphide bonds may serve an antioxidant role in the protection against Reactive Oxygen Species (ROS), often produced during aerobic metabolism in environments characterized by fluctuating oxygen and pH conditions.
