Methylene blue makes heart cell power plants produce more harmful molecules when using one fuel (glutamate/malate), but less when using another (succinate), showing its effect depends on what the cell is burning.
Scientific Claim
In isolated rat heart mitochondria, 0.1 µM methylene blue increases hydrogen peroxide production when respiration is driven by complex I substrates (glutamate/malate) but decreases it when driven by complex II substrates (succinate + rotenone), demonstrating a substrate-dependent dual effect on oxidative stress.
Original Statement
“Interestingly, methylene blue elicited a significant increase in H₂O₂ release in the presence of complex I substrates (glutamate and malate), but had an opposite effect in mitochondria energized with complex II substrate (succinate).”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
definitive
Can make definitive causal claims
Assessment Explanation
The study directly measured H₂O₂ levels under controlled substrate conditions; the bidirectional effect is empirically observed and statistically significant, justifying definitive language.
Evidence from Studies
Supporting (1)
Methylene blue makes heart mitochondria produce more hydrogen peroxide when they use one type of fuel (glutamate/malate) but less when they use another (succinate), showing its effect depends on what the mitochondria are eating.