The Different Level Of Methemoglobin And NADH-Cytochrome B5 Reductase In Training And Exhaustive Rat

Oxyhemoglobin is intrinsically unstable, and it oxidizes readily to methemoglobin (MetHb). At first, the ferrous iron center (Fe2+) of the heme moiety loses an electron to oxygen to produce a superoxide radical (O2"). This reaction simultaneously converts the iron center into its ferric (Fe3+) form to yield MetHb, the nonfunctioning form of Hb, according to the expression Fe2+ + O2- Fe3+ + O2-. Normally, in the red blood cell (RBC), superoxide is reduced back to oxygen via MetHb reductase and the ferric iron center back to its 2+ state: Fe3+ +O2- + MetHb reductase - Fe2++O2.An equilibrium between Hb and MetHb in red blood cells is well maintained due to the presence of enzymatic and non-enzymatic mechanisms. This equilibrium is disturbed when the red blood cells are exposed to some pathological and physiological stress, resulting in increased MetHb. Elevated levels of MetHb in blood are undesirable, as it impairs the normal physiological functions of hemoglobin, eg. oxygen transportation, etc.The present study was undertaken to estimate the levels of MetHb and NADH-Cytb5R in the red blood cell in different conditions. The results obtained show a significant increase in MetHb level in exhaustive rat. On the contrary, MetHb reductase, NADH-Cytb5R activities were found to be noticeably suppressed in exhaustive rat. The level of MetHb in exhaustive rat and the level of NADH-Cytb5R mRNA in traning rat both significantly increased compared with the resting rat.