Oxidation of human and animal haemoglobins with ascorbate, acetylphenylhydrazine, nitrite, and hydrogen peroxide.

This research studied the differences in susceptibility to oxidation of various types of haemoglobin (from humans, horses, cats and dogs) when exposed to specific oxidants. The results highlighted that susceptibility to oxidation varies by species and by type of oxidant, suggesting that an oxidant intermediate is important in haemoglobin oxidation triggered by certain drugs.

Methodology and Experiment Conditions

• The researchers used partially purified haemoglobin solutions from different mammals: human, horse, cat, and dog.
• The oxidation process was carried out using different oxidizing agents: ascorbate, acetylphenylhydrazine, nitrite, and hydrogen peroxide (H2O2).
• The experiments were conducted at two different temperatures: 25 degrees Celsius and 37 degrees Celsius. Notably, H2O2 and nitrite were only used at 25 degrees Celsius.

Differences in Oxidation Susceptibility Among Species

• Overall, the haemoglobins from carnivorous creatures (cats and dogs) were found to be more susceptible to oxidation than the haemoglobins from humans and horses.
• Sporting particular vulnerability was the feline haemoglobin, especially regarding oxidative denaturation — a process in which the protein loses its structure and function due to oxidation.
• At 37 degrees Celsius, the observations suggested that one form of feline haemoglobin (referred to as “B”) might be easier to oxidatively denature than another form (haemoglobin “A”).
• Horse haemoglobins were found to be the least prone to oxidation when ascorbate and nitrite were used. However, they were more easily oxidized by acetylphenylhydrazine than human or dog haemoglobins.

Implications Regarding Oxidant Susceptibility and Oxidation Triggers

• This research unveils that a haemoglobin’s susceptibility to one oxidant does not necessarily indicate its susceptibility to all oxidants. Therefore, the interaction between haemoglobin and an oxidant is not a straightforward relationship, and it’s influenced by more than just the oxidant’s presence.
• Findings from this study support the idea that an “oxidant intermediate” — a substance formed during the reaction between haemoglobin and an oxidant — might play a crucial role in haemoglobin oxidation caused by certain drugs, rather than the oxidant H2O2 itself.