His argument is that another biochemical mechanism explains metabolic acidosis associated with raised lactate. In the conversion of pyruvate into lactate, a hydrogen ion is consumedand this should in fact alkalinise the intracellular fluid. The cause of the metabolic acidosis in states usually related with raised lactate is actually the increased rate of ATP turnover which lowers pH.
Marik referred to Robergs et al in support of this, which is a study of exercising muscle. The authors performed a thorough review of lactate biochemistry, and ultimately concluded that lactate is an innocent bystander and that the hydrolysis of ATP is responsible for the acidosis.
This has a rather solid foundation in biochemistry. If we are going to talk in terms of protons, then it has long been known that lactate synthesis in anaerobic glycolysis is not a source of them.
The excellent article by Zilva was pillaged and his molecular representation of ATP hydrolysis reproduced here with no permission whatsoever. Ergo, in anaerobic metabolism, the total cost of energy production is in fact acidosis, but the production of lactic acid per se is not the cause of it. The inorganic phosphate removed from ATP is generally expected to buffer the "free proton" generated by this process, and it is then incorporated into aerobic metabolism to roduce more ATP.
During normal metabolism, something like moles of hydrogen ions are recycled in this manner over 24 hours Kreb, However, as the phosphate ion is rapidly recycled to produce more ATP particularly in "stressed" metabolically active tissues this buffering and recycling does not occur.
The net production of ATP i. In summary, tissues which have a high rate of ATP turnover are going to generate an acidosis. Lactate production occurs by processes which are usually associated with increased ATP turnover, and may therefore be proportional to the acidosis, but it is not causally linked to it - so Robergs et al argue.
It is pretty difficult to refute the point made by Robergs et al. If increased ATP hydrolysis and increased lactate production are caused by the same process, then metabolic acidosis and hyperlactataemia will occur together, at least some of the time. Logically, this position supports situations where there is raised lactate and no acidosis because there is no increased ATP hydrolysis.
Theoretically there should be disease states with increased ATP hydrolysis but no hyperlactatemia. However, states which are known to cause severe metabolic acidosis and hyperlactataemia aren't always associated with any sort of change in ATP hydrolysis. In fact there is good data that in severe sepsis ATP hydrolysis does not seem to increase. The sheep were injected with E. Fortunately quiet a few other authors did.
There is a significant amount of literature where investigators consistently fail to find an association between lactate, acidosis and bioenergetic failure. Choosing randomly from a massive pile of search results, one can identify highly cited articles such as the one by Hotchkiss and Karl Tons of septic rat data is presented where the rise in lactate was not associated with any cellular metabolic evidence of tissue bioenergetic failure.
This old article pre-dates more modern data which suggests that hyperlactataemia in septic shock may be more related to the inhibitory effects of cytokines and endotoxin on pyruvate dehydrogenase activity Crouser, Tying an elastic band around the arm may also have this result. For these reasons, the lactic acidosis blood test is sometimes done by finding a vein on the back of the hand instead of the arm. The best way to treat lactic acidosis is by treating its root cause.
For that reason, treatments vary. Lactic acidosis sometimes represents a medical emergency. This requires treating symptoms, regardless of their root cause. Increasing oxygen to the tissues and giving IV fluids are often used to reduce lactic acid levels.
Lactic acidosis caused by exercising can be treated at home. Electrolyte-replacement sports drinks, such as Gatorade, help with hydration, but water is usually best.
Based on the root cause, treatments for lactic acidosis often result in full recovery, particularly if treatment is immediate. Sometimes, kidney failure or respiratory failure may result. When left untreated, lactic acidosis can be fatal. Lactic acidosis prevention is also determined by its potential cause. If you have diabetes, HIV, or cancer, discuss your condition and the medications you need with your doctor. Lactic acidosis from exercise can be prevented by remaining hydrated and providing yourself with long resting periods between exercise sessions.
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However, during very intense exercise above steady state or during high-intensity resistance training , an accumulation of protons occurs in the muscle due to a much greater involvement of the phosphagen and glycolytic energy systems providing ATP for the muscle contraction. Robergs et al. What about Lactate Production and the Role of Lactate? During the demands of high-intensity exercise, the cell is utilizing a lot of glucose from glycolysis and muscle glycogen stored form of glucose. The final step of glucose breakdown results in the production of two molecules of pyruvate.
The pyruvate molecules begin to accumulate in the cell, as well as the protons from the splitting of ATP from the vigorous exercise. In order to neutralize the soaring accumulation of pyruvate and protons from the splitting of ATP , each pyruvate molecule absorbs two protons into its structure, converting to lactate. Lactate production is therefore good and not bad for contracting muscle.
Lactate is not a bad molecule, and it has been given a bad rap from being falsely blamed for the cause of acidosis. Personal trainers and fitness professionals can utilize this contemporary understanding of acidosis information for endurance and resistance exercise design.
Optimize Endurance Training, Volume 14 Number 1 pp For optimizing clients and students doing high-intensity resistance exercise, fitness professionals are encouraged to also incorporate endurance exercise in the training design. This important training addition will eventually lead to a better proton buffering capacity for the exercisers, thus inhibiting a major contributing factor to fatigue when they do their challenging resistance exercise workouts. Acidosis Question Box 1.
What is the Difference in Lactic Acid and Lactate? Although used interchangeable, lactic acid and lactate are not the same compound. Rather, lactate is the product of a side reaction in glycolysis. Acidosis Question Box 2. The fuel for this energy demand comes primarily from the anaerobic metabolism phosphagen and glycolytic energy systems.
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